Nervous Tissue

August 8, 2010

• Overview of the nervous system

• Cells of the nervous system

• Electrophysiology of neurons

• Synapses

• Neural integration

Subdivisions of the Nervous System

Two major anatomical subdivisions

• Central nervous system (CNS)

– brain & spinal cord enclosed in bony coverings

• Peripheral nervous system (PNS)

– nerve = bundle of nerve fibers in connective tissue

– ganglion

Subdivisions of the Nervous System

• Sensory (afferent) divisions (receptors to CNS)

– visceral sensory division

– somatic sensory division

• Motor (efferent) division (CNS to effectors)

– visceral motor division (ANS)

effectors: cardiac, smooth muscle, glands

• sympathetic division (action)

• parasympathetic division (digestion)

– somatic motor division

effectors: skeletal muscle

Fundamental Types of Neurons

• Sensory (afferent) neurons

– receptors detect changes in body and external environment

– this information is transmitted into brain or spinal cord

• Interneurons (association neurons)

– lie between sensory & motor pathways in CNS

– 90% of our neurons are interneurons

– process, store & retrieve information

• Motor (efferent) neuron

– send signals out to muscles & gland cells

organs that carry out responses called effectors

 

Fundamental Types of Neurons

Fundamental Properties of Neurons

• Excitability (irritability)

– ability to respond to changes in the body and external environment called stimuli

• Conductivity

– produce traveling electrical signals

• Secretion

– when electrical signal reaches end of nerve fiber, a chemical neurotransmitter is secreted

Structure of a Neuron

• Cell body = perikaryon= soma

– single, central nucleus with large nucleolus

 

– cytoskeleton of microtubules & neurofibrils (bundles of actin filaments)

• compartmentalizes RER into Nissl bodies

– lipofuscin product of breakdown of
worn-out organelles -- more with age

• Vast number of short dendrites

– for receiving signals

• Singe axon (nerve fiber) arising from axon hillock for rapid conduction

– axoplasm & axolemma & synaptic vesicles

Variation in Neuronal Structure

• Multipolar neuron

– most common

– many dendrites/one axon

• Bipolar neuron

– one dendrite/one axon

– olfactory, retina, ear

• Unipolar neuron

– sensory from skin & organs to spinal cord

• Anaxonic neuron

– many dendrites/no axon

– help in visual processes

Axonal Transport

• Many proteins made in soma must be transported to axon & axon terminal

– repair axolemma, for gated ion channel proteins, as enzymes or neurotransmitters

• Fast anterograde axonal transport

– either direction up to 400 mm/day for organelles, enzymes, vesicles & small molecules

• Fast retrograde for recycled materials & pathogens

• Slow axonal transport or axoplasmic flow

– moves cytoskeletal & new axoplasm at 10 mm/day during repair & regeneration in damaged axons

Six Types of Neuroglial Cells

• Oligodendrocytes form myelin sheaths in CNS

– each wraps processes around many nerve fibers

• Astrocytes

– contribute to BBB & regulate composition of brain tissue fluid

– most abundant glial cells - form framework of CNS

– sclerosis – damaged neurons replace by hardened mass of astrocytes

• Ependymal cells line cavities & produce CSF

• Microglia (macrophages) formed from monocytes

– concentrate in areas of infection, trauma or stroke

• Schwann cells myelinate fibers of PNS

• Satellite cells with uncertain function

Neuroglial Cells of CNS

Myelin Sheath

• Insulating layer around a nerve fiber

– oligodendrocytes in CNS & schwann cells in PNS

– formed from wrappings of plasma membrane

• 20% protein & 80 % lipid (looks white)

• In PNS, hundreds of layers wrap axon

– the outermost coil is schwann cell (neurilemma)

– covered by basement membrane & endoneurium

• In CNS, no neurilemma or endoneurium

• Gaps between myelin segments are known as Nodes of Ranvier

• Initial segment (area before 1st schwann cell) & axon hillock form trigger zone where signals begin

Myelin Sheath

• Note: The Nodes of Ranvier are located between Schwann cells

Unmyelinated Axons

• Schwann cells hold small nerve fibers in grooves on their surface with only one membrane wrapping

Speed of Nerve Signal

 

• Speed of signal transmission along nerve fibers

• Functions

– slow signals supply the stomach & dilate pupil

– fast signals supply skeletal muscles & transport sensory signals for vision & balance

Regeneration of Peripheral Nerve Fibers

• Can occur if soma & neurilemmal tube is intact

• Stranded end of axon & myelin sheath degenerate

• Healthy axon stub puts out several sprouts

• Tube guides lucky sprout back to its original destination

Electrical Potentials & Currents

• Neuron doctrine -- nerve pathway is not a continuous “wire” but a series of separate cells

• Neuronal communication is based on mechanisms for producing electrical potentials & currents

– electrical potential - difference in concentration of charged particles between different parts of the cell

– electrical current - flow of charged particles from one point to another within the cell

• Living cells are polarized

– resting membrane potential is -70 mV with a relatively negative charge on the inside of nerve cell membranes

Resting Membrane Potential

• Unequal electrolytes distribution between ECF/ICF

– diffusion of ions down their concentration gradients

– selective permeability of plasma membrane

– electrical attraction of cations and anions

• Explanation for -70 mV resting potential

– membrane very permeable to K⁺

• leaks out until electrical gradient created attracts it back in

– cytoplasmic anions can not escape due to size or charge (PO₄^2-, SO₄^2-, organic acids, proteins)

^– membrane much less permeable to Na⁺

– Na⁺/K⁺ pumps out 3 Na⁺ for every 2 K⁺ it brings in

• works continuously & requires great deal of ATP

Ionic Basis of Resting Membrane Potential

• Na⁺ concentrated outside of cell (ECF)

• K⁺ concentrated inside cell (ICF)

Local Potentials

• Local disturbances in membrane potential

– occur when neuron is stimulated by chemicals, light, heat or mechanical disturbance

– depolarization decreases potential across cell membrane due to opening of gated Na⁺ channels

• Na⁺ rushes in down concentration and electrical gradients

• Na⁺ diffuses for short distance inside membrane producing a change in voltage called a local potential

• Differences from action potential

– are graded (vary in magnitude with stimulus strength)

– are decremental (get weaker the farther they spread)

– are reversible as K⁺ diffuses out of cell

– can be either excitatory or inhibitory (hyperpolarize)

Chemical Excitation

Action Potentials

• More dramatic change in membrane produced where high density of voltage-gated channels occur

– trigger zone has 500 channels/mm² (normal is 75)

• If threshold potential (-55mV) is reached voltage-gated Na⁺ channels open (Na⁺ enters causing depolarization)

• Passes 0 mV & Na⁺ channels close (peaks at +35)

• K⁺ gates fully open, K⁺ exits

– no longer opposed by

electrical gradient

– until repolarization occurs

• Negative overshoot produces
hyperpolarization

Action Potentials

• Called a spike

• Characteristics of AP

– follows an all-or-none law

• voltage gates either open or don’t

– nondecremental (do not get weaker with distance)

– irreversible (once started goes to completion and can not be stopped)

The Refractory Period

• Period of resistance to stimulation

• Absolute refractory period

– as long as Na⁺ gates are open

– no stimulus will trigger AP

• Relative refractory period

– as long as K⁺ gates are open

– only especially strong
stimulus will trigger new AP

• Refractory period is occurring only to a small patch of membrane at one time (quickly recovers)

Impulse Conduction in Unmyelinated Fibers

• Threshold voltage in trigger zone begins impulse

• Nerve signal (impulse) - a chain reaction of sequential opening of voltage-gated Na⁺ channels down entire length of axon

• Nerve signal (nondecremental) travels at 2m/sec

Saltatory Conduction in Myelinated Fibers

• Voltage-gated channels needed for APs

– fewer than 25 per mm² in myelin-covered regions

up to 12,000 per mm² in nodes of Ranvier

^• Fast Na+ diffusion occurs between nodes

Saltatory Conduction of Myelinated Fiber

• Notice how the action potentials jump from node of Ranvier to node of Ranvier.

Synapses Between Two Neurons

• First neuron in path releases neurotransmitter onto second neuron that responds to it

– 1st neuron is presynaptic neuron

– 2nd neuron is postsynaptic neuron

• Synapse may be axodendritic, axosomatic or axoaxonic

• Number of synapses on postsynaptic cell are variable

– 8000 on spinal motor neuron

– 100,000 on neuron in cerebellum

Chemical Synapse Structure

• Presynaptic neurons have synaptic vesicles with neurotransmitter and postsynaptic have receptors

Types of Neurotransmitters

• 100 neurotransmitter types in 4 major categories

• Acetylcholine

– formed from acetic acid & choline

• Amino acid neurotransmitters

• Monoamines

– synthesized by replacing -COOH in amino acids with another functional group

– catecholamines (epi, NE & dopamine)

– indolamines (serotonin & histamine)

• Neuropeptides (next)

Neuropeptides

• Chains of 2 to 40 amino acids

• Stored in axon terminal as
larger secretory granules
(called dense-core vesicles)

• Act at lower concentrations

• Longer lasting effects

• Some released from nonneural tissue

– gut-brain peptides cause food cravings

• Some function as hormones

– modify actions of neurotransmitters

 

Excitatory Adrenergic Synapse

Cessation & Modification of the Signal

• Mechanisms to turn off stimulation

– diffusion of neurotransmitter away from synapse into ECF where astrocytes return it to the neurons

– synaptic knob reabsorbs amino acids and monoamines by endocytosis & breaks them down with monoamine oxidase

– acetylcholinesterase degrades ACh in the synaptic cleft

• choline reabsorbed & recycled

• Neuromodulators modify synaptic transmission

– raise or lower number of receptors

– alter neurotransmitter release, synthesis or breakdown

• nitric oxide stimulates neurotransmitter release

Neural Integration

• The more synapses a neuron has the greater its information-processing capability

– cells in cerebral cortex with 40,000 synapses

– cerebral cortex estimated to contain 100 trillion synapses

• Chemical synapses are decision-making components of the nervous system

– ability to process, store & recall information is due to neural integration

• Neural integration is based on types of postsynaptic potentials produced by neurotransmitters

Postsynaptic Potentials

• Excitatory postsynaptic potentials (EPSP)

– a positive voltage change causing postsynaptic cell to be more likely to fire

• result from Na+ flowing into the cell

– glutamate & aspartate are excitatory neurotransmitters

• Inhibitory postsynaptic potentials (IPSP)

– a negative voltage change causing postsynaptic cell to be less likely to fire (hyperpolarize)

• result of Cl- flowing into the cell or K+ leaving the cell

– glycine & GABA are inhibitory neurotransmitters

• ACh & norepinephrine vary depending on cell

Postsynaptic Potentials

Summation of Postsynaptic Potentials

• Net postsynaptic potentials in the trigger zone

– whether neuron fires depends on net input of other cells

• typical EPSP has a voltage of 0.5 mV & lasts 20 msec

• a typical neuron would need 30 EPSPs to reach threshold

– temporal summation occurs
when single synapse receives
many EPSPs in a short period
of time

• Qualitative information depend on:

– strong stimuli excite different neurons (recruitment)

– stronger stimuli causes a more rapid firing rate

• CNS judges stimulus strength from firing frequency of sensory neurons

– 600 action potentials/sec instead of 6 per second

Neuronal Pools and Circuits

• Neuronal pool is 1000’s to millions of interneurons that share a specific body function

– control rhythm of breathing

• Facilitated versus discharge zones

– in discharge zone, a single cell can produce firing

– in facilitated zone, single cell can only make it easier for the postsynaptic cell to fire

Neuronal Circuits

• Diverging circuit -- one cell synapses on another that each synapse on many others

• Converging circuit -- input from many fibers on one neuron (respiratory center)

Neuronal Circuits

• Reverberating circuits

– neurons stimulate each other in linear sequence but one cell restimulates the first cell to start the process all over

• Parallel after-discharge circuits

– input neuron stimulates several pathways which stimulate the output neuron to go on firing for longer time after input has truly stopped

Immediate Memory

• Ability to hold something in your thoughts for just a few seconds

Short-Term Memory

• Lasts from a few seconds to several hours

Long-Term Memory

• May last up to a lifetime

Alzheimer Disease

• 100,000 deaths/year

– 11% of population over 65; 47% by age 85

• Symptoms

– memory loss for recent events, moody, combative, lose ability to talk, walk, and eat

• Diagnosis confirmed at autopsy

– atrophy of gyri (folds) in cerebral cortex

– neurofibrillary tangles & senile plaques

• Degeneration of cholinergic neurons & deficiency of ACh and nerve growth factors

• Genetic connection confirmed for some forms

Parkinson Disease

Somatosensory Receptors:

· Most receptors are located in the skin – convert a stimulus into a receptor potential à can trigger an action potential

 

Female Reproductive System

July 29, 2010

Ovaries

 

• Deep in lower part of abdominal cavity
• 2 inches long, 1 inch wide
• several ligaments that hold them in place

 

1 ovarian ligament – attaches ovaries to uterus

 

2 suspensory ligament – attaches ovaries to pelvic wall

3 mesovarian ligament – stabilizes the ovaries in between the other ligaments

 

 

Structure

 

Outer Cortex

Inner Medulla

 

• interspersed in the cortex are many egg sacs called ovarian follicle
• all at different stages of development
• when baby girl is born ~ 2 million follicles are present ~ by the time she reaches puberty, 400,000 follicles remain.

 

Stages

 

1 Primary follicle – inside these follicles are a primary oocyte (immature egg)

and granulosa which contains 46 chromosomes

 

2 undergoes 1^st miotic division into –

 

secondary oocyte and a polar body

/ \

23 chromosomes (also 23 chromsomes)

receives most of the cytoplasm ends up dying

located in secondary follicle

 

Secondary follicle has grown larger from filling up with fluid

 

3 Grafian follicle – mature egg which is full of fluid and will burst which then

releases the egg (ovulation)

 

The follicle that just ovulated – once it loses its egg – ‘corpus luteum’

 

There is no fertilization…then corpus leuteum will degenerate in about 10 days

If fertilization occurs, the corpus leuteum will remain and act like a gland and

secrete estrogen and progesterone

 

 

Duct System

Near each ovary, but not connected to it is the Fallopian tube (uterine tube)

At the distal end of the uterine tube, there is a funnel shaped structure

(Infundibulum) – finger-like projections called Fimbriae

 

The egg gets into fallopian tube by:

Fimbriae – they sweep it into the tube

Uterine tube is linked with cilia – egg is drawn in.

Implants into abdominal wall – ectopic pregnancy

Ectopic pregnancy is egg inplantation anywhere but inside the uterus.

 

The egg moves through the uterine tube by contractions and cilia.

The uterine tube contains three layers:

Outer serous membrane

Middle muscular

Inner epithelium

If sperm are present in the uterine tube, the egg gets fertilized.

Fertilization occurs around 24hours after ovulation.

 

 

Uterus

• very thick, muscular walls
• pear shaped
• located above the urinary bladder

 

Embryo develops in uterus

The uterus when empty is approximately two inches

It can stretch to 12 inches within the nine month pregnancy period

 

 

Sections

1 superior portion – fundus

2 central portion – body

3 punched in portion – isthmus

4 inferior portion – cervix

 

Layers

• outer serous layer – perimetrium
• muscular middle layer – myometrium
• inner most layer – endometrium

 

 

Ligaments attached to Uterus

 

1 pair of broad ligaments

· attaches uterus to body wall

· goes right across pelvic cavity

 

2 pair of round ligaments

· attach uterus to labia majora

 

3 pair of uterosacral ligaments

· attaches uterus to sacrum

 

4 posterior ligament

· attaches uterus to rectum

 

5 anterior ligament

· attaches uterus to bladder

 

 

Endometrium – helps to form placenta

· cancer of the cervix

· pap smear test to detect it

· histarectomy – removal of the uterus

· oovectomy – removal of ovaries

 

uterus opens bordered by the cervix into the vagina – birth canal

 

 

Vagina – 3 layers

 

1 outer fibrous layer

2 muscular layer

3 mucosa – inner layer

 

Rugae are transverse

Opening of Vagina – vaginal orifice (which is partly covered by a membrane

known as the hymen)

Imperferate hymen – doctor will remove hymen if blocking menstrual flow

 

 

External Genitals

Collectively called Vulva

Consists of: two flaps of skin on either side of the vaginal opening.

- externally called labia majora

- internally called labia minora

Together they protect the urinary and genital openings.

 

The Labia meet anteriorly to form the hood of skin to cover over the clitoris

The clitoris is similar to the penis. After about two months of development, the

sex gene turns on that area and decides whether it will turn into a penis or clitoris

 

Female Orgasm:

Muscles surrounding the vagina contract and there is an increase in

uterine motility….this aids sperm by increasing their movement

superiorly towards uterus and fallopian tubes.

 

The reproductive and urinary systems are separate in the female.

(compared to the male urethra which is used for both semen and urin)

 

 

Mammary Glands – Breasts

 

· each breast is subdivided into 15-25 lobules

· many small alveoli in each lobule

· there are secretory cells in the alveoli which secrete milk

From the alveoli, the milk will flow through secondary tubules…as they are moving towards the nipple, several secondary tubules will merge to form a

lactiferous duct. Right before the nipple, the lactiferous duct becomes a

lactiferous sinus which carries milk to the nipple.

 

• Colostrum produced during pregnancy
• Two hormones – estrogen and progesterone inhibit the action of prolactin (lactogenic hormone)
• Once a woman has given birth, the nerve endings within the nipple become more sensitive – sucking from the infant sends impulses to hypothalamus – causes secretion of Prolactin (milk production) and Oxytocin (release of milk)
• It takes a few days after delivery for milk production to begin, producing colostrum (protein rich as well as a great source of passive immunity)

 

 

Hormonal Regulation

 

Hypothalamus stimulates GnRH to stimulate adenohypophysis to secrete FSH &

LH. FSH stimulates follicle – secretes estrogen. LH will form corpus luteum –

secretes progesterone

 

If level of estrogen is increased, then a negative feedback loop stops stimulating

the adenohypophysis from making FSH.

 

 

Estrogen is responsible for:

1 stimulates growth of uterus, vagina, and breasts.

2 for eggs to mature

3 more body fat

4 bigger pelvic girdle

 

 

Progesterone is responsible for:

1 breast and uterus development

2 prepares uterus for implantation

 

2 Gonadotropic and 2 Sex Hormones are secreted at different rates.

Compared to a male always has same amount of testosterone in blood stream.

 

 

Ovarian Cycle

1-28 days

 

Phase 1 – Follicular phase

FSH is secreted by adenohypophysis that causes one ovarian follicle to mature.

Follicle will be secreting estrogen.

 

 

Phase 2

 

Around fourteenth day, ovulation occurs

Level of estrogen increases which causes pituitary to diminish secretion of FSH

Body will begin secreting LH

 

 

 

Phase 3 – Luteal phase

Occurs after ovulation

Secretion of LH causes the ruptured follicle to become corpus luteum

Corpus luteum secretes progesterone which increases in the blood

Pituitary will diminish secretion of LH

 

 

 

 

Uterine Cycle

1-28 days

 

Days 1-5

Low levels of estrogen & progesterone when it has decreased levels, affects the

Endometrium and starts to break – blood vessels rupture and you get flow of

Blood – menses passes out of vagina. (menstrual phase)

 

Days 6-13

Increased production of estrogen coming from the growing follicle.

Endometrium starts to thicken and blood vessels and glands form and are growing

(proliferative phase)

 

Day 14

Ovulation occurs

 

Days 15-28

Increase in progesterone level from corpus luteum

The endometrium is doubling in thickness

Uterine glands mature and produce thick mucus (secretory phase)

Endometrium is now prepared to receive a fertilized egg

 

If female does not become pregnant, the corpus luteum degenerates and progesterone

level will decrease. Both sex hormones are at low levels. At the end of this, will go

back to days 1-5

 

 

Menopause

Cessation of menstrual cycle

Occurs between ages of 45 – 55

After 20, the ovaries will not respond as well to hormones (FSH & LH)

Estrogen level decreases throughout life

Menstrual cycle gets irregular when reaching menopause and then finally stops

 

 

Symptoms:

· Hot flashes

· Depression

· Insomnia

· Headaches

Control of Reproduction

3 major areas of birth control research

 

1 Morning after Pill

A chemical DES – acts by preventing implantation

nausea and vomiting

sons have highest rate of testicular cancer with women who have used

DES.

 

B RU486 – causing the lining of uterus come out.

Form of abortion

 

2 Longer duration of methods

A Depoprovera – injectable, inhibits follicles development

Injected every 3 months

B Norplant – implantable material – hormone that is like progesterone

Last for 5 years and interferes with ovulation

 

3 Male pill

in the U.S. no research is being conducted

will interfere with production of sperm

 

 

Infertility

Inability to produce offspring

 

In women:

Failure to ovulate.

Fertility drugs are recommended by some OB’s

One side effect is multiple pregnancies

 

Obstruction can occur which prevents sperm from getting to the egg

Embryo can die before implantation

 

 

Alternative Reproduction Methods

 

1 artficial insemination

- sperm placed in vagina by physician

- usually use husband sperm, or could have a donor

 

2 Invitro Fertilization

- 1978 – 1^st test tube baby

- remove an egg from mothers ovary and transfer egg that is prepared in a sterile medium and introduce fathers sperm & fertilize the egg

- it develops in the lab for 2-4 days and then is introduced into the mother in secretory phase (when the uterus is well prepared for the egg to be implanted)

 

3 GIFT – gamete intrafallopian transfer

- as soon as sperm fertilizes the egg, they put in egg into the

fallopian tube

4 Serogate mother

- women that are paid to except sperm

- can also receive an egg of another woman

 

 

 

^{Reproductive Physiology}

^Testes

• ^{Also known as testicles}
• ^{About 5 cm long and 2 ½ cm in diameter}
• ^{Outside of abdominal cavity in a sac of skin called the scrotum}

^{- b/c it’s cooler (about 3 degrees cooler than the abdominopelvic cavity}

^{- best temperature for sperm production and storage}

^{2 layers in wall of scrotum}

^{- dermal layer à Dartos tunic}

^{- inside layer (muscular) à cremaster muscle}

^{muscle helps control the temp. of scrotum.}

^{- relaxation results in descent}

^{- contraction results in ascent}

^{Descent of Testes}

• ^{develop in fetus in abdominal cavity adjacent to kidneys}
• ^{right before birth they descend (lower) into scrotum (last month or two b/f birth)}
• ^{as they lower you have blood vessels, lymphatic vessels, nerves – all of this together make up the spermatic cord (suspending the testes)}

^{If Testes do no descend this is known as cyrptocordism}

^{Surgery is required.  If this doesn’t occur, the male will be sterile because there}

^{is too much heat in the abdominopelvic cavity}

^{they pass through inguinal canal on descent}

^{this is an area of weakness.  Can get a hernia in this area}

^{Testes surrounded by a tough fibrous capsule called tunica albuginea}

^{They are divided into lobules (250-300)}

^{Each lobule there are one to three tightly folded (coiled) seminiferous tubules}

^{Stages of sperm development take place here – spermatogenesis}

^Stages

^{Cells called spermatagonia – undifferentiated germ cell}

^{A germ cell is a cell that will give rise to other types of cells}

^{Spermatagonia have 46 chromosomes}

^{They undergo cell division:}

^{Mitosis – only used for growth and repair of body}

^{Meiosis – only to produce gametes (sperm and eggs)}

^{Meiosis Cell Division}

^{1st miotic division to become 2 secondary spermatocytes}

^{(each one has 23 chromosomes)}

^{The two Secondary undergo a 2nd miotic division each to form two spermatids}

^{(each contain 23 chromosomes)}

^{Once sperm are produced they leave the seminephris tubules and swim through straight}

^{Tubules and get to rete testis – network of tubules and leave through an efferent duct}

^{They finally get to the epididymis where the sperm mature into spermatozoa.}

^{(spermatozoa are mature sperm)}

^{Sperm Anatomy}

^{One cell}

^Head

^{Is the nucleus – where the 23 chromosomes reside}

^{The tip of the head has an acrosome – a protective structure which contains an enzyme}

^{The enzyme is called hyaluronidase, which they need to penetrate the ‘egg’}

^{Mid Piece}

^{Where mitochondria live - to supply sperm with energy.}

^Tail

^{Consists of a Flagella which are made of microtubules}

^{The tail is responsible for motility}

^{The sperm leave the epididymis through a tube – ductus deferens}

^{The Ductus Deferens goes into abdominal cavity by way of inguinal canal.}

^{Enlarges to form ampulla.  It will join a duct coming out of seminal vesicle.}

^{Once they join it is called the ejaculatory duct.}

^{The sperm move through the duct work by peristalsis action.}

^Vasectomy

^{A surgery that involves making an incision into the scrotum and surgeon takes a hook}

^{to pull out the ductus deferens and is then cut and then reinserted back into the}

^scrotum.

^{Ejaculatory duct join with the urethra at the prostate.}

^Urethra

^{Has three parts.}

^{1 Prostatic – passes through the prostate}

^{2 membranous – through opening – urogenital diaphram}

^{3 penile (spongy) – passing through penis (the longest part)}

^{The urethra is 7 – 8 cm long}

^{Accessory Glands}

^{There are three types that each contribute to secretion}

^{1 Seminal Vesicles – little sacs near the base of the bladder.}

^{- produces solution that contains fructose (energy for sperm)}

^{- also contains prostaglandins -causes uterin contraction & pushes sperm up}

^{2 Prostate – surrounds urethra and produces a milky alkaline solution to aid in motility}

^{3 Bulbourethral glands (2 of them) – pea sized gland produces mucous secretion that}

^{serves as a lubricant.}

^{When you total all the secretions from the three glands and the sperm, you have semen.}

^{pH of Semen is between 7.35 and 7.50  (slightly alkaline)}

^{this is going to neutralize the acid of the urethra.}

^{The vagina is also acidic – so this helps to neutralize it.}

^Penis

^{Contains three cylindrical masses of erectile tissue}

^{Two dorsal masses (corpora cavernosa)}

^{One ventral mass – corpus spongiosum}

^{The are numerous blood vessels}

^{When the penis is in a flaccid / resting state, the blood vessels are constricted.}

^{Under parasympathetic stimulation, all blood vessels are dilated.}

^{Increase in blood flow produces the male erection}

^{An erection is maintained due to close proximity of arteries and veins.  When the   arteries and arterioles are filled with blood they press up against the veins and}

^{venules so the blood is unable to leave.}

^{Impotence – failure of the penis to achieve erection}

^{The penis is covered with smooth skin.  A circumcision is when the foreskin is}

^{Surgically removed shortly after birth.}

^{Semen is expelled out of the male through the male orgasm.  All secretions come out}

^{and duct work contracts all contents enter the urethra.}

^{The sphinctor at the base of the bladder constricts so that urine is unable to escape.}

^{After male orgasm – (refractory or latent period) unable to have another orgasm}

^{Hormones – hormonal regulation}

^{Hypothalamus secretes GnRH – stimulates adenohypophysis to produce 2 hormones}

^{Gonadotropic hormones – LH  and FSH}

^Targets:

^{FSH – stimulates seminiferous tubules to produce sperm}

^{LH – stimulates interstitial cells to produce testosterone}

^{Testosterone is responsible for:}

^{1 development and functioning of sex organs}

^{2 for sperm to mature}

^{3 males greater strength}

^{4 responsible for}

^{Prostatitis – inflammation of prostate.}

^{The urethra travels through prostate and urination could be painful.}

^{Impotency – can not achieve an erection}

^{Sterility – can not fertilize an egg (from low or abnormal sperm count)}

^{Sexually Transmitted Diseases}

^{1 Genital Herpes – caused by type II herpes simplex virus.}

^{Begins as a rash – get anywhere from 2 to 20 days after}

^{exposure.  It then disappears and the}

^{virus remains dormant.  Contagious when}

^{you have lesions or rash.  Biggest danger is}

^{to babies ~ a third of babies die when caught}

^{disease during birth.  No Cure.}

^{2 Gonorrhea – (neisseria gonorrhea) – males have a burning sensation during}

^{mictruation. They also have a discharge.}

^{Leads to sterility.  Babies can become blind}

^{3 Chlamydia Trachomatis –  most men do not know if they have this or gonorrhea}

^{Chlamydia is the most common cause of inflammation in the testicles and sperm-conducting tubes (epididymo-orchitis) in men under 35. This causes marked pain, swelling and redness in the scrotum on the affected side, or on both sides. Chlamydia infection can also trigger joint inflammation in some men.  Leads to sterility.}

^{4 Treponema Pallidum (syphyllis) has three stages}

^{1` painless lesion: chancre (usually at the entry of body) heals quickly}

^{2` organism has entered bloodstream (flu-like symptoms) Lasts for years.}

^{3` permanent neurological damage.  heart damage.  TXed with antibiotics}

^{5 AIDS – caused by HIV:  attacks T helper cells;  inactivates your ability to}

^{produce antibodies.  Transmitted through blood}

^{contact, sexually, needles.}

^Stages:

^{1 find antibodies n bloodstream}

^{2 ARC – Aids related complex: fatigue, fever, cachexia, diarrhea}

^{3 AIDS – severely immunocompromised.  Minor infections that our bodies fight}

^{naturally and with no problem can easily kill an AIDS pt.}

^{Drug – AZT azidothymidine – interferes with cell division – tries to prevent}

^{virus from multiplying.}

 

 

Renal Physiology

7/19/2010

 

 

 

Urinary System

2 kidneys, 2 ureters, 1 urinary bladder, 1 urethra

 

 

Kidneys

· Bean shaped

· In a depression against deep muscles of the back

· Retroperitoneal

· Getting some protection from the ribcage

· Approximately 4 inches long and 2 inches wide

 

 

· Surrounded by tough fibrous tissue – Renal Capsule

· Adipose Tissue surrounds the Capsule

· Renal Fascia – anchoring kidneys to body wall

3 Layers

 

1 Cortex – outer layer --- granular in appearance

2 Medulla – inner layer --- striated appearance

3 Renal Pelvis – where urine will collect before the ureter

 

Conical masses of tissue in Medulla are Renal Pyramids

- Apex of pyramid is the Papilla

 

 

Renal Pelvis divides into 2-3 major Calyxes which subdivide into minor Calyxes

(minor calyxes enclose the papilla {tips of pyramids})

 

 

Blood Supply

 

 

- Renal Artery that enters each kidney

divides in Medulla and become Interlobar Arteries

Interlobar divide into Arcuate Arteries ( at the boundary b/t cortex and

medulla.

Arcuate arteries become interlobular arteries (extend deep into cortex)

 

 

Arterioles, capillaries, venules, interlobular, arcuate, and then interlobar vein

 

Nephrons – (kidney tubule)

- functional unit of kidney

- about 1 million in each kidney

 

 

 

5 Parts:

 

1 Bowmans Capsule – cup shaped structure; inside is mass of capillary called

Glomerulus.

o afferent arteriole --- blood enters

o efferent arteriole --- blood leaves

 

2 layers of cells – outer layer is squamous epithelium

inner layer is podocytes

 

 

2 Proximal Convoluted Tubule – near the Bowmans Capsule: has many microvilli

 

 

3 Loop of Henle

 

 

4 Distal Convoluted Tubule

 

 

5 Collecting Duct – receives urine from several nephrons

 

 

 

Cortex is granular because of Bowman’s capsules and convoluted tubules.

Medulla is striated because of Loop of Henle and collecting ducts

 

 

Juxtaglomerular Apparatus

2 parts of nephron touch each other

consists of 2 kinds of cells

1 on outside of afferent – juxtaglomerular cells

2 large cells on distal convoluted tubule – maculadensa cells

 

where maculadensa and juxtaglomerular cells touch

is called the juxtaglomerular apparatus

 

 

 

 

 

Kidney Physiology

 

Urine Formation

 

• occurs in 3 steps
• process 180 Liters (45G) of blood / fluid through kidneys per day (24 hours)
• down to 1.5 Liters of Urine

 

 

 

Step: 1 Glomerular Filtration

• substances pass from blood to nephron
• when blood enters glomerulus the pressure = 60 mmHg

diameter of afferent is greater than diameter of efferent, so pressure of

blood builds up

 

 

 

2 opposing pressure

A: osmotic pressure – created by plasma proteins = 32 mmHg

B: capsular pressure – resistance to the flow of fluids in the capsule = 18

mmHg

 

o Blood Pressure is still higher than 2 opposing pressures

o Only certain substances can leave the blood

 

 

 

Net Filtration Pressure = 10 mmHg

Net Filtration Rate

(how much coming out of blood every min.)

120-125 ml/min à 180 L. (Filtrate [coming out of blood] )

 

 

What should be prevented from entering urine? Blood, blood proteins

 

What will enter filtrate? Water, nitrogen wastes, nutrients, and salts

 

Nervous system (sympathetic) could constrict both afferent + efferent arterioles?

- Urine decreases

 

Happens in emergencies + stress --- want blood to be shunted to heart, brain, etc.

 

 

 

 

Step 2 Tubular Reabsorption

 

· Reducing the 180 L down

· Opposite of step 1

· Return substances back to blood

· Peritubular capillary network – surrounds the tubule

· Filtrate moves into PCT

 

 

 

2 kinds of Transport:

active

passive

 

 

 

Returned to bloodstream (Reabsorbed)

~ 80% of H2O returned

- glucose

- amino acids and salts

- vitamins, minerals, and nutrients

- have a lot of microvilli to increase surface area for greater reabsorption

Active Transport – glucose, salts, amino acids

Passive Transport – water

 

 

 

Costs energy --- in walls of Proximal Convoluted Tubule are Mitochondria

The walls have protein carrier molecules – pick up substances in filtrate and are

returned to the blood

 

 

 

 

Renal Threshold

• if concentration of substance exceeds a certain level you do not reabsorb the excess

 

 

ex. glucose (has an increase Renal Threshold) means you’re going to reabsorb

most of it.

 

 

ex. urea (has a decreased renal threshold) all will stay in filtrate

 

 

 

- Filtrate moves to the Loop of Henle (down) and even more water gets reabsorbed from the filtrate

- Filtrate getting more and more hypertonic (concentrated)

 

 

Step 3 Tubular Secretion

• Opposite of step 2
• Substances added to urine

 

What can get added to urine? Uric acid, ammonia, creatinine, histamine

(even penicillin) coming out of blood into urin

 

- more water gets reabsorbed

- Hydrogen ions (pH: 7.35 – 7.45)

 

- tend to accumulate hydrogen in blood

- greater source --- cellular respiration

 

 

Horomone ADH – target is Kidney’s which causes cells in DCT and collecting

duct to become more permeable to water. Reabsorbs water back into blood stream which will produce less urine

 

Diuretics block ADH – to make you produce more urine.

Characteristics of Urine

Yellow, amber color – due to urochrome breakdown product of Hgb.

Intensity, vitamins, etc. … effect color, smell

Turbid – urine standing around becomes cloudy due to bacteria. (it oxidizes the

properties of urea and produces ammonia) pH is 4.5 – 8.0

Liver converts ammonia to urea.

Specific Gravity – relative measure of weight of given liquids.

 

1.000 – distilled water

1.001 – 1.030 – urine

95 % of urine is water. 5 % nitrogen, wastes, and salts

- our metabolism produces nitrogen wastes, ammonia, uric acid, urea, creatinine

 

 

Urine goes into the renal pelvis and then to ureters which extend from the Hilum of

Kidney to the bladder

 

 

Layers of Ureter

- outer fibrous layer

- middle muscular layer – peristalsis moves urine down ureters

- transitional epithelium

 

 

 

Urinary Bladder

- hollow organ, walls are easily stretched.

- Has 4 layers

o Outer fibrous

o Middle muscular

o Transitional epithelium

o Submucosa

 

- bladder when empty – 2.5” long

- bladder when full – 5” long

 

 

 

contains 3 openings

o 2 for ureters

o 1 for urethra

 

- Trigone connects 3 openings – it doesn’t do anything - sphincters + ureter

 

 

Urethra

· 2 sphincters

* internal – involuntary keeps bladder closed

* external – voluntary

 

- extends from bladder to external urethral orifice

 

· 1” long in female

· 7-8” long in male – prostate surrounds male urethra; it can enlarge and prevent urination.

· Male urethra delivers both semen and urine

 

 

 

Urination (Mictruition)

q Stretch receptors in wall of bladder

q Parasympathetic nerve brings impulse to muscle wall of bladder; bladder contracts (impulse continues) contractions continue, contractions cause internal sphinctor to relax

 

 

 

Problems with Urination

 

1 Incontinence – involuntary control; inability to control release of urine (normal

in infants) In Adults, this is due to stress and/or nerve damage

 

 

2 Urine Retention – retaining urine caused by lack of nerve stimulus

 

 

 

Kidney stones (uretolithiasis) runs in families, not drinking enough water.

Take ultrasound waves and blast the stones into smaller fragments – lithotripsy

 

 

UTI – urinary tract infection

Urethritis – inflammation of urethra

Cystitis – inflammation of bladder

Nephronitis – inflammation of kidney

 

 

Urinalysis – analysis

Urinalysis is the testing of the physical characteristics and composition of freshly voided urine.

A U/A will allow you to look for the following:

• Urine appearance and color (for example, clear, cloudy, turbid, layered; pale yellow, dark yellow, red, green, blue)
• Bilirubin - urine (a degradation product of hemoglobin)
• Glucose (a sugar) -- should not be found in urine
• Hemoglobin (an indication of hemolysis)
• Urine ketones (a by-product of fat metabolism and present in starvation and diabetes)
• Nitrite (an indication of urinary tract infection)
• Urine pH (the acidity or alkalinity of the urine)
• Urine protein
• Urine specific gravity (that is, how concentrated or dilute the urine is)
• Urobilinogen (a degradation product of bilirubin)

Uremia – urea is accumulating in blood

Paruresis – psychological disorder --- difficulty urinating in front of other people

 

Kidney Replacements:

 

1 Transplant – receive functioning kidney from a donor

 

2 Dialysis:

A. Kidney machine

Blood pumped out of patients artery and put into dialysis solution

(semi-permeable membrane tubing): only certain substances pass

out of blood go into solution (salts, etc.) cleaning your blood

Could put glucose in solution if pt. is low in glucose

(3 times a week)

 

 

B. CAPD – continuous ambulatory peritoneal dialysis

o Inject dialysis solution into patients abdominal cavity and left for 6 hours than drained

o High risk

 

 

 

 

 

 

Metabolism – all of chemical reactions that occur within the body

 

Anabolic – Requires Energy

 

 

Catabolic – Releases Energy

 

 

 

Cellular Respiration -- the process of oxidizing food molecules, like glucose, to carbon dioxide and water. The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.

 

The body cannot synthesize vitamins and minerals – they must be obtained through

diet

 

A Protein that speeds up any reaction is an Enzyme

An Enzyme that contains an extra portion to it that is not a protein, is a CoEnzyme

(co·en·zyme) (ko-en¢z[imacr]m) an organic nonprotein molecule, frequently a phosphorylated derivative of a water-soluble vitamin, that binds with the protein molecule (apoenzyme) to form the active enzyme (holoenzyme).

 

 

2 CoEnzymes

NAD: contains the vitamin niacin

FAD: contains the vitamin Riboflavin

 

Oxidation – the loss of Hydrogens

Reduction – the gaining of Hydrogens

 

NAD – has been oxidized

NADH – has been reduced

 

 

ATP

- energy

- when you break a bond, you release energy (ATP à ADP + Pi)

- Phosphorylation – transfer of a phosphate (receiving a phosphate)

 

 

ATP Cycle

ATP à ADP + Pi releases energy

 

To make ATP, you have to add Phosphate and it also requires energy

(comes from cellular respiration which occurs in the Mitochondria)

 

General Equation for Cellular Respiration

 

Glucose + Oxygen à CO2 + H2O + ATP

C6H12O6 + O2 à CO2 + H2O + ATP

 

 

Carbohydrate Metabolism

To break down Glucose

 

4 steps:

 

 

1 Glycolysis --- process in which Glucose is broken down into 2 molecules of

Pyruvic Acid

The 1^st two steps are a Phosphorylation RXN

 

• Glucose gains phosphate from ATP (using ATP) Phosphorylation occurs twice
• Splits into 2 molecules of PGAL of 3 Carbons each
• PGAL – 2 molecules gets oxidized – NAD comes in and leaves as NADH – when this occurs, energy (ATP) is released as 2 molecules. 1 Molecule of PGAL = 2 ATP formed and also 2 molecules of Pyruvic Acid
• ** 1 molecule of C6H12O6 à net ATP = 2 ; gross ATP = 4

 

 

 

 

 

 

 

 

 

 

 

 

 

2 Formation of Acetyl CoEnzyme A

{you need to know if O2 was available or not to determine what happens to

Pyruvic acid}

 

 

 

 

 

 

3 Krebs Cycle (Citric Acid Cycle)

 

• acetyl CoA -- into Krebs cycle
• step after step – citric acid will be oxidized; NAD comes in and leaves as NADH
• if you keep oxidizing Citric Acid, the product is Oxaloacetic acid
• CO2 given off as a byproduct
• 1 ATP is produced

 

ATP produced during Krebs cycle is 2 ATP

2 Pyruvic Acid to 2 Acetyl CoEnzyme A – this would make 2 ATP

 

Oxidative decarboxylation means the pyruvate is oxidized (by removal of H) & decarboxylated by removal of CO2.

4 Electron Transport (oxidative phosphorylation)

 

• Mitochondria – contains 2 membranes
• Inner membrane contains cristae
• Step 4 occurs on the Cristae (have carrier molecules that carry the hydrogen)
• NADH comes in and leaves as NAD – it leaves H+ with carrier molecules
• Also the FADH comes in and leaves as FAD (leaves the H+)

 

 

 

 

 

Lipid Metabolism

 

Lipids – composed of 3 Fatty Acids and 1 Glycerol

Glycerol converted PGAL – pyruvic acid à acetyl Co-A à TCA cycle

 

Fatty Acids:

- break down by Beta-Oxidation (occurs in cell)

- acetyl CoEnzyme A – is put into TCA cycle

 

 

- 1 Fatty Acid molecule produces 148 ATP (148 ATP x 3 F.A. = 444 ATP)

 

- Lipogenesis à stores as adipose

- Break down of stored fat as a source of energy à Lypolysis

- Lypolysis à byproduct of Ketones ( a buildup of ketones is Ketosis)

- Ketosis leads to acidosis (now blood pH falls below 7.35)

- (breath smells fruity because of this)

 

 

 

Protein Metabolism

- broken down amino acid + delivered to all your cells and you make protein out of amino acid

 

 

Protein --- Amino Acids (cannot be stored)

If getting too much protein à extra amino acids

 

Amino Acids are broken down by Transamination and then by Deamination

One by-product is Ammonia --- the Liver converts ammonia to urea and the

Kidneys excrete it.

Atkins à enough carbs in 2 slices of toast which is enough to feed one tenth

of what your brain needs

 

 

 

Bioenergetics

Mitochondria – 43 % efficient (get out of glucose)

 

- cars are 10% efficient

- light bulbs are 5% efficient The rest is given off as Heat

 

 

How good is your personal metabolism

 

Determining Metabolic Rate

1 Room Temp must by comfortable - 20 – 25` C

2 Person must be reclining and at rest

3 Person is at rest Mentally

4 Must be in post absorptive state – cannot be digesting food. Didn’t eat for last 12-14

hours

 

· get measurement BMR (Basal Metabolic Rate)

· In general women have a better BMR

· Hormone that affects BMR the most is Thyroxine

 

 

 

Weight gain – caloric intake more than your BMR + physical activity

Weight loss – consume less calories than what you burn 3500 calories = 1 pound

Thermoregulation

· Regulation of body temperture

· Average human body temp 98.6` F or 37` C

· Warmest temp – core (deepest inside skull, thoracic, and abdominal cavities)

· Coolest temp. – shell (skin)

· One degree higher than oral temp. is rectal temp.

· Daily variations – lowest temp between 3 –5 a.m. and peak around 4 p.m. (highest) than you start cooling down again

· We have a very constant body temp. because we maintain a balance between Thermogenesis (heat production) and Thermolysis (heat loss)

 

· Part of Brain responsible for this balance is the Hypothalamus

Sympathetic (Heat gain center)

Divisions of Autonomic Nervous System

Parasympathetic (Heat loss center)

 

· Getting information about body temp. through thermoreceptors (peripheral {skin} and central)

 

 

 

 

4 Heat Promoting Mechanisms

 

1 vasoconstriction – decreased blood flow to skin

 

2 increased metabolic rate – by hormone Epinephrine

 

3 shivering thermogenesis – increase in muscle tone

 

4 Thyroxine – increased metabolic rate of all your cells

 

 

 

 

4 Heat Loss Mechanisms

 

1 Radiation – heat travels from hot to cold

 

2 Conduction – transfer of heat through direct contact

 

3 Convection – losing heat to the air

 

4 Evaporation – when water evaporates it takes heat with it

 

 

 

 

Digestion

 

 

Digestion – breakdown of complex food materials into simpler forms

Gut – synonym for digestive tract

 

 

1 alimentary canal – (digestive tract) from mouth to anus

2 accessory organs – help the digestive process –

6 Digestive Processes

1 ingestion – food enters mouth

2 propulsion (peristalisis) – how food moves through the system

3 mechanical digestion – like teeth chewing food

4 chemical digestion – chemical breakdown of food

5 absorption

6 defication – elimination

 

4 Layers of Tract

 

1 serosa – outer membrane covering secretes serous or watery lubricant

Serosa comes from the Mesentary. It is continuous with the serosa

2 muscularis externa – smooth muscle – has two layers of muscle

- outer layer of muscular fibers run longitudinal

- inner layer of fibers are circular around the organ

3 submucosa – may see blood vessels, lymphatic vessels, a nerve plexus, and maybe

a gland that secretes lubricated mucous into the lumen

 

4 mucosa – secretes mucous

 

 

3 Layers of Mucosa

 

1 muscularis

2 lamina propria

3 epithelium – all kinds of modifications done here

 

 

Mouth

 

32 Teeth found in an Adult mouth

12 molars

8 bicuspids (premolars)

4 cuspids (canines)

8 incisors

canine (also called cuspid) - the pointy tooth located between the incisors and the premolars. A canine tooth has 1 root. Adults have 4 canine teeth (2 in the top jaw and 2 in the bottom jaw). Canine means, "of or like a dog."
incisors - the front teeth, used for cutting food. An incisor has 1 root. Adults have 8 incisors (4 in the top jaw and 4 in the bottom jaw).
premolars (also called bicuspids) - the teeth located between the canine and the molars. A premolar tooth has 1 root. Bicuspids have two points (cusps) at the top. Adults have 8 premolars (4 in the top jaw and 4 in the bottom jaw).
molars - the relatively flat teeth located towards the back of the mouth, used for grinding food.

Tooth Structure

 

Enamel – Ca+ compound – outside

Dentin – Middle part – where bone is

Pulp – inner part that also contains nerves, lymphatic vessels, blood – mass of

Loose C.T.

 

 

Gingivitis – inflammation of the gums

Periodonditis - Periodonditis is a dental disorder that results from progression of gingivitis, involving inflammation and infection of the ligaments and bones that support the teeth.

 

Periodontal diseases (commonly known as "gum diseases") affect one-third of the U.S. population. There are 2 common forms of periodontal disease. The first, gingivitis, is a reversible inflammatory process that is confined to gum tissues. While gingivitis is unsightly and is characterized by red, bleeding gums, it does not involve the destruction of the supporting structures of the teeth and can often be controlled by close attention to oral hygiene as well as the use of OTC toothpastes and prescription antibacterial mouthwashes.

Of much more concern is periodontitis, which can arise following gingivitis if the infection and inflammation remain untreated, particularly in patients with certain genetic traits, in those who have certain systemic diseases such as diabetes and osteoporosis or who engage in activities such as smoking which result in increased susceptibility. Periodontitis is a disease initiated by bacterial infection.

 

 

Anterior part of the mouth – hard palate made up of palatine bone and palatine process

of maxilla

Hard and Soft palate --- ends at uvula

Soft Palate and uvula posterior to hard palate --

 

Salivary glands – 3 pair secrete saliva into the mouth through ducts

 

Pair of Parotid Glands – on the side of the face just below the ears

Pair of Sublingual glands – below tongue

Pair of Submaxillary glands – below jaw

 

Saliva consists primarily of H2O and Mucous

Salivary Amylase – digestive enzyme breaks down starch found in saliva; secreted by

Salivary glands – Starch (polysaccharide) found in Saliva breaks

down to Maltose

Polysaccharide breaks down to disaccharide

You make 1 and a half quarts saliva/day

 

 

Tongue

 

Big Muscle – on upper surface are bumps called papillae (very sensitive to touch)

In the center (a trench)

Between papillae running among trenches are taste buds

 

Food must be in solution in order to taste it

Anything you eat must be in solution (molecules in solution go down into the

Trenches to the taste buds – molecules must go to taste pores – then the

 

 

Basic Taste – taste buds are localized

Salty – tip

Sweet – right behind the tip

Sour – area on the sides

Bitter – posterior portion

 

 

 

Pharynx – located between mouth and esophagus

 

Epiglottis – flap of tissue, when you swallow, the epiglottis lowers to cover the trachea

You cannot breathe when you swallow

 

Esophagus – closed at all times except when swallowing food

 

Food in mouth is shaped by tongue – rounded to bolus. Tongue pushes food back

down to Esophagus

Same 4 layers as discussed before

Esophagus very muscular because it performs Peristalsis – rhythmic contraction

that pushes food along

Esophagus goes down the thoracic cavity through the diaphram to the stomach

 

Hiatal Hernia

 

Can develop one by pushing or straining too much when trying to have a bowel

movement.

Bolus of food goes down esophagus and pushed there by waves of peristalsis.

Pushes food inferior --- spinchtor at entrance of stomach (GastroEsophageal

Sphintor) Normally the spinctor is closed. You don’t want food coming back up.

As Peristalsis relaxes sphintor, it opens.

Vomitting is Reverse Peristalsis

 

Stomach

 

- thick muscular walls

- holds 2 liters

- greater curvature – convex shape

- lesser curvature – concave shape

 

4 Regions

 

1 Cardiac region –

 

2 Fundus –

 

3 Body –

 

4 Pylorus –

 

-

- 3 layers of muscle

- deep folds on inner mucosa = Rugae – the rugae allow for stomach to expand; distensibility

- Inner mucous membrane

§ Interrupted by pits (gastric pits)

§ Lined by columnar epithelium

§ Go down into pit and open into gastric gland

 

4 Glands (Gastric) Cells

 

 

1 mucous neck cells –

2 chief cells –

3 parietal cells –

4 enteroendocrine cells –

 

- bolus – arrives at stomach and is mixed for about 4 hours with gastric juice.

 

- Pyloric sphinctor controls food out of stomach into the duodenum

 

 

Regulations of Gastric Emptying

 

• Stomach has been stretched and this stimulates stretch receptors. This triggers afferent nerve impulses through the Vagus.

1 doesn’t want to get big chunks of fat

2 the longer chyme stays in the stomach the less acidic it gets

 

 

Small Intestines

- about 20 feet long, and 1 inch in diameter

- divided into 3 regions:

 

 

1^st Region Duodenum – 12 inches

chyme mixed with 2 secretions:

 

1^st secretion Liver – producing Bile – then stored in Gall Bladder --- from G.B., Bile travels through Cystic duct and into Common Bile duct, which merges with the Pancreatic duct just prior to entering the Duodenum

 

 

2^nd secretion added to chyme is Pancreatic Juice. Pancreatic duct leaves

the pancreas merges with the Common Bile duct before entering the

descending portion of the duodenum

Pancreatic juice – contains 3 enzymes

 

 

2^nd Region Jejunum – 8 feet

 

3^rd Region Ileum -- 12 feet

 

 

Chyme moving through intestines and in the wall of S.I. is filled with intestinal

glands, which produce intestinal juice (enzymes)

 

Enzymes of intestinal juice:

1 peptidase – breaks proteins into amino acids

 

 

2 lactase – breaks down lactose in glucose and galactose

 

Osteoporosis - can also occur from an increase in animal protein consumption; kidneys

secrete extra calcium (loosing calcium)

 

Lining of Small Intestine?

 

Fingerlike projections – villi

They have their own villi – microvilli for greater absorption;

increase in surface area

 

Absorption – is absorbed into the epithelium

 

Villi – inside there is a blood capillary and each has a lymphatic vessel called a

Lacteal

Fats cannot get into capillary, but will be absorbed into lacteal the fluid inside is lymph

Lymph gets into circulatory system carrying all the fat you ingested.

Ileum – Pyers Patches – keep control of bacteria (ends in the ileocecal valve)

 

 

Large Intestines

About 5 feet long

 

4 Regions

 

1 Cecum 2 Colon – has 4 regions

1 Ascending

2 Transverse

3 Descending

4 Sigmoid

 

3 Rectum

 

4 Anal Canal – opens into anus

 

No enzymes produced in Large Intestines. Principal function is to absorb HOH

 

Disorders

Diarrhea – too much water in L.I. (not enough absorption of water)

Constipation – not enough water in L.I. (too much absorption of water)

 

Feces – whatever is unabsorbed /undigested fills up large intestines

1/3 of weight of feces – bacteria

Polyps – can be cancerous and be removed or they may remove parts or all of colon

Colostomy – rectum sewed up and patients wears a bag

 

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Risk Factors for Colon CA

Ethnic background

A personal history of colorectal cancer and or colorectal polyps

A personal history of chronic inflammatory bowel disease

Aging

A diet mostly from animal sources

Physical inactivity

Obesity

Diabetes

Smoking

Alcohol intake

Night shift work

 

 

Accessory Organs

I Liver à blood containing what you ate goes to liver through the Hepatic Portal Vein

located towards upper right side of Abdominal Cavity

4 Lobes of the Liver:

1 Right

2 Left

3 Caudate

4 Quadrate

 

 

6 Main Functions

 

1 destroys RBC’s (old ones) Hgb broken down into Bilirubin & Billiverden.

2 produces bile which emulsifies fat

 

3 Produces glycogen from glucose and stores it. When the body needs glucose

(especially between meals) then liver breaks glycogen back down to glucose

 

 

4 produces urea; from the break-down of A.A.

 

 

5 produces blood proteins: Albumin

Globulin

Fibrinogen

 

6 detoxifies the blood (alcohol, drugs, etc.)

 

 

 

The Liver

• The liver secretes bile. Between meals it accumulates in the gall bladder. When food, especially when it contains fat, enters the duodenum

 

 

The hepatic portal system

The capillary beds of most tissues drain into veins that lead directly back to the heart. But blood draining the intestines is an exception. The veins draining the intestine lead to a second set of capillary beds in the liver. Here the liver removes many of the materials that were absorbed by the intestine:

The liver serves as a gatekeeper between the intestines and the general circulation. It screens blood reaching it in the hepatic portal system so that its composition when it leaves will be close to normal for the body.

 

 

Disorders:

 

1 Jaundice – skin and eyes turn yellow due to accumulation of bilirubin in blood

(serves as a sign of a disorder)

 

 

2 Cirrhosis – chronic disease; a fatty liver due to excess alcohol consumption

 

 

3 Gallstones – aka Cholelithiasis – blockage of Cystic, Common Hepatic, or

Common Bile ducts by a hardened substance. Stones are usually made up of

cholesterol from diets.

 

 

Although newborns are the most frequent victims, adults also get jaundice, a yellow discoloration of the skin and the whites of the eyes. Jaundice is not a disease in itself. Usually it signals some type of liver damage---such as hepatitis (an inflammation of the liver) or cirrhosis (a slow deterioration of the liver)---or an obstruction in the ducts that drain bile from the liver.

Risks

The amount of risk this condition presents depends upon its underlying cause. However, any type of liver malfunction should be taken seriously. If left untreated, it could lead to liver failure.

 

II Gallbladder

- pear shaped sac; located anterior inferior surface of Right lobe of Liver

- stores bile by concentrating it

 

 

Gallstones are small, hard pellets that can form in the gallbladder, a sac-like organ that lies under the liver on the right side of the abdomen. Most people with gallstones dont even know they have them. But in some cases a stone may cause the gallbladder to become inflamed, resulting in pain, infection, or other serious complications.

 

III Pancreas

 

- located retroperitoneally in the abdominal cavity

o islets of Langerhans – endocrine glandular tissue. Produces hormones Insulin and Glucagon

o acini cells – exocrine tissue - produce pancreatic juices

o The pancreas consists of clusters of endocrine cells (the islets of Langerhans) and exocrine cells whose secretions drain into the duodenum.

 

 

Food Groups

 

 

Carbohydrates – broken down in mouth and ends up as glucose in the duodenum

 

 

 

Lipids – chemical digestion begins in Duodenum and ends there. Broken down

Into Glycerol and Fatty Acids

 

 

 

Proteins – digestion continues in stomach (its broken down into Amino Acids)

and continues in the duodenum

The stomach continues physical break-down and begins chemical break-down by secreting a substance called pepsinogen. It then converts pepsinogen into an enzyme called pepsin. This enzyme starts to break apart the protein into amino acids.