FINAL EXAM Flashcards
function of digestive system?
-process food, extract nutrients, and eliminate waste
5 stages digestive system
- ingestion
- digestion- chemical and mechanical breakdown of food
- absorption- the uptake of nutrients into the epithelial cells of the digestive tract and then into the blood or lymph
- compaction- absorbing water and consolidating the waste
- defecation
organs that make up digestive tract
-mouth
-pharynx
-esophagus
-stomach
-small intestine
-large intestine
accessory organs digestive tract
-teeth
-tongue
-salivary glands
-liver
-gallbladder
-pancreas
functions of the stomach
-food storage organ
-where the process of chemical digestion continues
-mechanically breaks up food
-produces watery mixture of semi-digested food called chyme
gastric pits
-the depressions in the gastric epithelium that are lined with simple columnar epithelial cells
-lead down into the gastric glands
-contain a variety of glandular cell types
gastric gland + types
-contain a variety of glandular cell types
1. mucous cells
2. parietal cells
3. chief cells
4. enteroendocrine cells
mucous cells
produce mucus
parietal cells
-secrete hydrochloric acid and when the stomach is empty, an appetite-stimulating hormone called ghrelin
-HCl breaks down food and helps destroy ingested pathogens. also produces intrinsic factor, which binds to vitamin B12 and allows for its absorption in the small intestine. –Vitamin B12 is needed for normal RBC production. Without intrinsic factor, anemia develops due to the inability to synthesize hemoglobin.
chief cells
-secrete gastric lipase and pepsinogen (pepsinogen gets converted to pepsin by HCl, which then digests proteins)
enteroendocrine cells
-secrete hormones and paracrine messengers that regulate digestion.
-at least 8 kinds of enteroendocrine cells in the stomach, and probably about 20 different chemicals messengers produced.
-G cells produce gastrin, which stimulates HCl release and increases gastric motility
how is the lining of the stomach protected?
- mucous coat
- tight junctions
- rapid cell replacement- the epithelial cells od the mucosa layer only last for 3-6 days
steps for regulation of gastric function:
- cephalic phase
- gastric phase
- intestinal phase
cephalic phase
-the stomach responds to the sight, smell, taste, or thought of food
-these inputs converge on the hypothalamus, which relays signals to the medulla. then the vagus nerve fibers stimulate the stomach to secret HCl and gastrin
-this phase prepares the stomach to receive food
gastric phase
-in this phase, food in the stomach and semidigested proteins activate gastric activity
-the stretch of the stomach activates responses that lead to the release of ACh from parasympathetic fibers, histamine from enteroendrocrine cells, and gastrin from G cells. all 3 stimulate the release of HCl, intrinsic factor, and pepsinogen
-the presence of amino acids also stimulates the release of gastrin
intestinal phase
-starts when chyme starts to arrive in the duodenum of the small intestine
-the presence of acid and semidigested fats in the
duodenum triggers the enterogastric reflex – the
duodenum a) sends signals via the nervous system
to the stomach, b) sends signals to the medulla to
inhibit vagal stimulation of the stomach, and c)
sends signals via sympathetic neurons to the
stomach. All of these serve to inhibit gastric function.
-enteroendocrine cells in the duodenum release secretin and cholecystokinin (CCK), both of which inhibit gastric secretion and motility
function of gallbladder:
stores bile until it is released into the small intestine via the common bile duct
where is bile initially secreted
from the liver
function of bile:
aids in digestion of fats.
-contents of bile act to separate fat molecules from one another so they do not form clumps
-allows lipase to digest the fat more efficiently
pancreas
-both an endocrine and exocrine organ
*endrocrine part is the pancreatic islets (islets of Langerhans)- secrete insulin and glucagon
*about 99% of the pancreas is exocrine tissue that produces pancreatic juice. it has acini that open into ducts that eventually converge into the main pancreatic duct, which carries materials to the small intestine
what makes up pancreatic juice?
-it’s an alkaline mixture
-contains water, electrolytes, sodium bicarbonate, and digestive enzymes (trypsinogen, chymotrypsinogen, procarboxypeptidase, pancreatic amylase, pancreatic lipase)
how is the release of pancreatic juice and bile regulated?
a. ACh- from the vagus nerve. causes secretion of pancreatic enzyme, even in anticipation of eating
b. cholecystokinin (CCK)- secreted by the SI in response to fats in the SI. strong effect on the release of bile; also causes secretion of pancreatic enzymes
c. secretin- secreted by the SI in response to acidity in the SI. causes an increase in the release of sodium bicarbonate from the pancreas to neutralize the acid
small intestine parts + function
-duodenum, jejunum, ileum
-duodenum is where secretion from gallbladder and pancreas are added to the chyme
-jejunum is where more digestion and nutrient absorption occur
-ileocecal sphincter separates SI and LI
structure and function of villi
-covered with absorptive cells and goblet cells, which produce mucus.
-increases surface area of inner lining of SI
-each villus contains and arteriole, capillaries, a venule, and a lacteal (which absorbs lipids)
what does the wall of the SI secrete?
-alkaline secretion (intestinal juice)
-mucus
function of intestinal motility
-mix chyme with intestinal juice, pancreatic juice, and bile
-churn the chyme to break it up mechanically and promote absorption
-move materials toward the large intestine
segmentation
contractions that target certain locations/sections in SI to further move material/break stuff up
migrating motor complex
when absorption of nutrients is mostly complete, the SI releases the hormone motilin, which causes waves of peristalsis called the migrating motor complex.
carb. digestion/absorption
-starch is digested into glucose, which is what gets absorbed by the SI
-about 50 % of starch is digested by the actions of salivary amylase and HCl from the stomach before it reaches the SI
-in the SI, pancreatic amylase (and some enzymes embedded in the wall of the SI) break down the rest of the starch into glucose
-sucrose and lactose are broken down by sucrase and lactase and the resulting monosaccharides (glucose and fructose, glucose and galactose) are absorbed
-the effectiveness of lactase diminishes with age in most individuals
-all the monosaccharides are absorbed by blood capillaries of the villi, and the hepatic portal vein transports them to the liver
protein digestion/absorption
-enzymes that digest proteins are called proteases. these include pepsin in the stomach and trypsin, chymotrypsin, carboxypeptidase, aminopeptidase, and dipeptidase in the SI
-amino acids are absorbed by blood capillaries of the villi, and the hepatic portal vein transports them to the liver
lipid digestion/absorption
-fats are digested by lipases. includes lingual lipase, gastric lipase, and pancreatic lipase. Only about 15% of lipids are digested by the time the chyme reaches the SI
-the churning of the stomach emulsifies the fats (breaks it up into smaller droplets)
-in the SI, these droplets are coated by lecithin and bile salts (to keep them from combining) and pancreatic lipase digests the lipids in the droplets
-pancreatic lipase breaks triglycerides down into a monoglyceride and two free fatty acids (making them easier to absorb)
-micelles, which consist of bile acids with the
hydrophobic portions facing inward and their
hydrophilic portions facing outward, will absorb the monglycerides and free fatty acids, in addition to cholesterol and fat-soluble vitamins. The micelles carry these lipids to the surface of the absorptive cells
-Inside the absorptive cells, the free fatty acids and monoglyceride are reformed into
tryglycerides, which are then placed into
packages called chylomicrons. The
chylomicrons are released from the absorptive cells and taken up by the lacteals
-From there, the lipids travel through the lymph system to be deposited in the circulatory system at the subclavian veins. Eventually they move to adipocytes for storage or to other body cells for
use in production of ATP.
large intestine function
-reabsorption of water and electrolytes
-compacts the waste into feces
female reproductive primary and secondary organs
-primary: ovaries
-secondary: internal reproductive tract (uterine tubes, uterus, and vagina) and external genitalia (clitoris, labia minora, labia majora)
ovary functions
-female gonads
-produce egg cells and sex hormones
*ovarian follicles each consist of one developing ovum (egg) surrounded by numerous small follicular cells
ovulation
eggs are released one at a time through the bursting of the follicles. the left and right ovaries alternate in activity from month to month.
uterus structure + function
-thick, muscular chamber that opens into the top of the vagina
-function of the uterus is to harbor the fetus, nourish it, and expel the fetus at the appropriate time
hormones released by hypothalamus and anterior pituitary gland
-in males, GnRH produced by the hypothalamus, and causes the release of LH and FSH from the anterior pituitary gland
what percentage of body fat is needed for hormonal axis activity?
-20%
-if leptin levels are too low, due to a low percentage of fat, then GnRH is not produced in adequate amounts and reproductive function will cease (or puberty will be delayed)
function of FSH
-FSH causes the development of ovarian follicles, which secrete estrogens, progesterone, inhibin, and low levels of androgens
main effect of progesterone
-acts primarily on the uterus, preparing it for potential pregnancy
-maintains a pregnancy
effects of estradiol
-causes growth of the ovaries and secondary sex organs
-stimulates growth hormone secretion, which leads to a rapid increase in height and widening of the pelvis
-stimulates fat deposition in the hips, thighs, buttocks, and breasts
effects of androgens in females
-responsible for growth of pubic and axillary hair and the development of sebaceous glands
hormones involved in negative feedback in hormonal control of function
-estrogen, progesterone, inhibin
oogenesis
-egg production!
-cyclic event that produces one egg per month usually
oogenesis steps
-begins before birth
-At that time, all oogonia initiate meiosis and become primary oocytes. Most of these primary oocytes undergo atresia before birth, but as many as 2 million remain at birth, and 200,000
at the start of puberty. This is more than enough, as fewer than 500 eggs are ovulated during a female’s lifetime
-then it is paused until puberty
-At puberty, once a month about two dozen of the primary oocytes are recruited to resume
development, a process that takes about 290
days (although usually only one of these
survives to be ovulated). During that time they
will undergo the rest of meiosis I (which
produces a polar body) and the start of meiosis
II. Meiosis II is not fully completed until
fertilization by a sperm occurs.
follicular development steps
1.Primordial Follicles – These consist of a primary oocyte surrounded by a single layer of
squamous cells. These are formed during
gestation but persist into adulthood as described above. These make up about 95% of
the follicles in an adult ovary. Again, once a month about two dozen of the primordial follicles are recruited to resume development.
2.Primary Follicles – By day 140, the two dozen
primordial follicles have become primary
follicles. The cells become cuboidal, and the
oocyte becomes larger
3. Secondary Follicles – By day 170, the follicular cells (now called granulosa cells) multiply into multiple layers. An outer layer of theca cells also develops. The larger oocyte is now surrounded by a glycoprotein gel called the
zona pellucida
4. Tertiary Follicles – The theca cells divide into a theca externa (made up of smooth muscle) and a theca interna (which produce steroids). LH stimulates the theca interna to absorb
cholesterol from the blood and convert it to
androgens. These diffuse into the granulosa
cells, where they are converted to estrogens,
especially estradiol. By day 230, the granulosa
cells secrete follicular fluid, which forms a pool
(called the antrum) inside the follicle.
5.Mature (Graafian) Follicles – Normally
only one follicle from each month’s cohort
becomes a fully mature follicle, which will
undergo ovulation
what hormone directs follicular development
FSH
components of the sexual cycle
ovarian and menstrual cycle
ovarian cycle phases
- follicular phase
- ovulation
- luteal phase
follicular phase
Extends from the beginning
of menstruation (Day 1) until ovulation (Day
14). During this time, FSH stimulates continued
growth of all follicles, but especially the
dominant one. FSH also stimulates the
secretion of estradiol from the granulosa cells.
At the end of this phase, there is a spike in LH
secretion (the LH surge). The LH causes an
increase in the production of follicular fluid,
which causes the follicle to swell and enlarge.
ovulation
Ovulation, which consists of a
bursting of the follicle due to the
increased pressure from the build-up of
follicular fluid, takes only a few minutes.
Normally, the egg, which is released from
the surface of the ovary, is taken up by
the uterine tube. However, it is not
unusual for oocytes to remain in the
pelvic cavity and die
luteal phase
Extends from ovulation until the end of
the cycle (Day 28). If pregnancy does not occur, the
following events takes place: Under the direction of LH,
the ovulated follicle becomes a structure called the
corpus luteum. LH stimulates the corpus luteum to
secrete both estradiol and, especially, progesterone.
The corpus luteum starts to shrink at about Day 22 and
by Day 26 has turned into a scar tissue called the
corpus albicans. Due to the reduction in estrogen and
progesterone levels near the end of this phase,
negative feedback on FSH production is relaxed, and
FSH levels begin to increase again to stimulate a new
cohort of follicles
menstrual cycle
-runs concurrently with the ovarian cycle and is dependent upon the release of hormones from the ovary.
-3 phases:
1. menstrual phase
2. proliferative phase
3. secretory phase
menstrual phase
As the functional layer
of the endometrium degenerates, it falls
away and mixes with blood to form
menstrual fluid. As this fluid accumulates,
it is discharged through the vagina. This
phase is also called menses
proliferative phase
This phase starts at
about Day 5. Estrogen that has been
secreted by the follicles stimulates mitosis
in the basal layer to cause the regrowth of
the functional layer. Estrogen also causes
the proliferation of blood vessels and
endometrial glands
secretory phase
The endometrium continues
to thicken, but mostly due to secretion and fluid
accumulation instead of mitosis. The number of
progesterone receptors in the endometrium
increases under the direction of estrogen, and
progesterone from the corpus luteum causes
the endometrial glands to grow and to secrete
glycogen and more fluid. Near the end of this
phase, the endometrium starts to degenerate
due to the fact that the corpus luteum in the
ovary has degenerated and is no longer
producing progesterone
syncytiotrophoblast secretes what hormone?
human chorionic gonadotropin (HCG)
-maintain the corpus luteum so it continues to produce large amounts of progesterone (basically prolongs life of corpus luteum)
corpus luteum
-disappears around 20 weeks of pregnancy
-releases estrogen and progesterone
what does the placenta do after the corpus luteum disappears?
take over the production of estrogens and progesterone
estrogen functions during pregnancy
stimulates tissue growth in the fetus. In the
mother, it causes the uterus and external genitalia to
enlarge, causes the mammary ducts to grow, and
causes the breasts to grow. It also makes the pubic
symphysis more elastic so that the pelvis can widen
during childbirth
progesterone functions pregnancy
suppresses uterine contractions so
early labor is not as likely to occur. It also
contributes to the development of the mammary
glands
functions of male reproductive system
produce sperm, introduce sperm into female body, produce steroid hormones
primary sex organs in males
the testes
secondary sex organs in males
penis, scrotum, vas deferens, prostate gland, bulbourethral glands, and seminal vesicles
where are sperm produced?
-inside coiled tubules called the seminiferous tubules
cells in the seminiferous tubules
-several layers of germ cells
-nurse cells (support the germ cells and produce androgen-binding protein and inhibin)
how is testosterone produced
testosterone is produced by the interstitial cells, also known as Leydig cells that are found in between the tubules
spermatogenesis
process of sperm formation achieved through meiosis (single diploid cell gives rise to four haploid cells)
-diploid cells called spermatogonia
-haploid cells called spermatids
-cells migrate thru the seminiferous tubes to the core
what must spermatids do?
transform into sperm!!! :D
parts of sperm + function
-flagellum
-mitochondria (power flagellum)
-acrosome (contains enzymes to penetrate the egg if contact is made)
-genetic material in the head
epididymis
-site of sperm maturation and storage
-sperm are moved along the fluid from the nurse cells and by the actions of cilia on the cells of ducts to get to the epididymis
vas deferens
transport sperm from epididymis to urethra
accessory glands that secrete materials that make up semen
-seminal vesicles
-prostate gland
-bulbourethral glands
functions of semen
-provides nutrients for the sperm in the form of sugars (fructose) and ions (calcium, phosphate, citrate)
-helps buffer acidic pH of the female reproductive tract
males hormones fetus
During the first trimester, the testes in the fetus
secrete large amounts of testosterone. Even
during the first few months after birth,
testosterone levels are as high as they are
during puberty. The purpose of elevated
testosterone at that time is to direct the
development of the internal and external
reproductive structures (the secondary sex
organs). After that, the testes become dormant
until puberty
males hormones puberty
As puberty begins, the hypothalamus produces
more GnRH gonadrotropin-releasing hormone),
which causes the release of LH (luteinizing
hormone) and FSH (follicle-stimulating hormone)
from the anterior pituitary.
* LH causes the interstitial cells to produce
testosterone. Testosterone promotes sperm
production. It also causes the development of
secondary sex characteristics, enhances libido
and promotes territorial and aggressive
behaviors
FSH stimulates the nurse cells to secrete
androgen-binding protein, which holds
testosterone in the seminiferous tubules.
* Nurse cells also secrete inhibin, which functions
in a negative feedback loop to inhibit the release
of FSH from the anterior pituitary.
* Testosterone has an inhibitory effect on the
release of GnRH.
anatomy
the study of the structures of living organisms
physiology
the study of how living organisms function
homeostasis
the maintenance of the relatively constant internal environment
negative feedback
-when any deviation from the set point is made smaller (resisting the change)
-ex. regulation of blood pressure, body temperature, and blood sugar levels
positive feedback
-when a deviation occurs, the response is to make the deviation greater (much less common than negative feedback)
-ex. childbirth, opening on sodium channels associated with action potentials, platelet-plug formation during blood clotting
Plasma Membrane
defines the boundaries of the cell, controls interactions with other cells, and controls movement of materials in and out of the cell
-appears as a pair of dark parallel lines
membrane proteins- receptors
-usually specific for one kind of chemical messenger
-chemical signals/messengers that cannot enter cell might bind to surface receptors
membrane proteins- enzymes
-some embedded proteins are enzymes that can catalyze certain reactions
membrane proteins- channel proteins
2 types: leak channels & gated channels
leak channels- always open
gated channels- may be ligand-gated, voltage gated, or mechanically gated
membrane proteins- carrier proteins
-transmembrane proteins that bind to glucose, electrolytes, and other solutes then transfer them to the other side of the membrane
-if they have to work against a concentration gradients, they’re called pump and they consume ATP
membrane proteins- cell-identity markers
-glycoproteins contribute to the glycocalyx, which enables the body to distinguish its own healthy cells from other things (diseased cells, invading organisms, etc.)
membrane proteins- cell-adhesion molecules
-allows cells to adhere to one another and to extracellular material
selective permeability def.
something can act as both a barrier and a pathway between the cytosol and extracellular fluid
rates of diffusion thru a membrane depend on: (5)
- temperature
- molecular weight of the molecule
- steepness of the concentration gradient
- membrane surface area
- membrane permeability to that molecule
what is facilitated diffusion?
-carrier-mediated transport of a solute thru a membrane down its concentration gradient
-no energy required!
what is active transport?
-a carrier protein moves a substance across a cell membrane against its concentration gradient
-energy (from ATP) is required!
functions of the sodium-potassium pump
- regulation of cell volume- more ions are pumped out than in, so it prevents cellular swelling
- maintenance of a membrane potential- the inside of the cell is more negatively charged than the outside
- heat production- heat is released as ATP is used for the pump
vesicular transport
-large amounts of material are moved inside bubble-like vesicles made of membrane
-endocytosis
-exocytosis
endocytosis
-phagocytosis
-pinocytosis
-receptor mediated endocytosis
how does the nervous system regulate internal functions?
- processing information about internal and external environments
- processing that info and determining if a response is necessary
- sending commands, mostly to muscle and glandular tissue, to carry out the responses
peripheral nervous system divisions are called…?
- sensory division/afferent division
- motor division/efferent division
myelin sheath
a spiral layer of insulation around a nerve fiber
-formed by oligodendrocytes in the CNS and by Schwann cells in the PNS
