GI + Reproductive Physiology Flashcards
1
Q
What is the function of the mouth for GI physiology?
A
- taste
- chewing (mixing food with saliva –> decreases size + mixes carbs w/salivary amylase) - bolus formation
- salivary glands: amylase (initial starch digestion) + lingual lipase (intial triglyceride digestion)
2
Q
What is the function of the esophagus?
A
- transport
- during swallowing (involuntary - medullary swalling center): soft palate elevates, epiglottis covers glottis, UE sphincter relaxes + food goes down)
3
Q
What is the function of the stomach?
A
- storage
- grinding
- mixing
- digestion
- secretion (acid)
- acid environment (pH1-2) enables activation of pepsinogen to pepsin
4
Q
What gets secreted in the stomach?
A
- Mucus cells: secrete mucus
- Chief cells: secrete pepsinogen (–> pepsin –> protein digestion)
- Parietal cells (secrete HCL, IF)
- ECL cells: secrete histamine
- G cells (secrete gastrin; gastric lipase)
5
Q
What are the digestive functions of the liver?
A
- metabolism
- detoxification
- catabolism of ammonia to urea (whole cycle)
- heme –> bilirubin –> +albumin
- bile production + secretion
(bile functions in lipid digestion + excretion)
6
Q
What is the digestive function of the gallbladder?
A
- bile storage
7
Q
What does the exocrine pancreas do?
A
- digestion
- HCO3 buffer
8
Q
What does the small intestine do?
A
- digestion + absorption (proteins to aas, carbs to monosacchs, fats to chylomicrons)
- duodenum: neutralizes gastric contents (HCO3 –> inactivates pepsin), absorbs iron, Ca, carbs, fats, proteins
- jejunum: net absorption of NaHCO3, also carbs, fats + prots
- ileum: net absoprtion of NaCl, Vit B12, also fats + proteins
9
Q
What does the large intestine do?
A
- fluid + electrolyte absorption
- segmented propulsion
- ascending (absorption of water + ion)
- transverse (fermentation)
- descending (storage of waste + indigestible materials)
10
Q
General GI Wall Structure
A
LUMEN (microvilli)
- mucosa: epithelium, bm, lamina propria, muscularis mucosa
- submucosa (innervated by nerves)
- muscularis propria: circular muscles, myenteric plexus (innervated by nerves), longitudinal muscle
- mesothelium (serosal surface)
SEROSA
11
Q
How is surface area increased in the gut?
A
- folds (3x)
- LI: villi (30X), crypts
- SI: microvilli (600x)
12
Q
How does the autonomic NS regulate GI fcn?
A
Intrinsic
- enteric NS in M + SP (can direct all GI fcn): input from PS/S nerves (modulates activity), mechano + chemorec
Extrinsic
- PS: excitatory, vagus + pelvic nerves (long pre + short post-ganglionic fibers) –> M + SP –> smooth muscle, secretory cells, endocrine cells of GI
- S: inhibitory, short pre + long post ganglionic fibers that go to M + SP or directly to bvs + smooth muscle cells
13
Q
What is the hormonal regulation of the GI system?
A
- endocrine: Gastrin, GIP, Secretin
- neurocine: Ach, vasoactive intesting polypetide, CCK
- paracrine: prostaglandins
14
Q
What does Gastrin do?
A
coordinates H+ secretion by parietal cells
15
Q
What does Secretin do?
A
- secreted by S cells of duodenum
- stimulated by H+, FA in duod.
- increases pancreatic secretion of HCO3
16
Q
What does GIP do?
A
aka glc-dependent insulotropic peptide
- secreted by K cells of duod + jej
- stimulated by all carbs, fats, + prots (only GI hormone that is)
- increases insulin secretion from pancreas
- decreases gastric H+ secretion
17
Q
What does CCK do?
A
- secreted by I cells of duod + jej
- stimulated by aas + FAs
- increases pancreatic secretions
- stims GB to contract (bile release)
- relaxes sphincter of Oddi
- inhibits gastric empyting
18
Q
What happens when you eat?
A
food in stomach –> increased acid secretion + motility –> food + acid in duod
–> CCK + secretin secretion –> pancreatic + biliary secretion –> intestinal digestion of foods
–> GIP secretion –> insulin secretion
19
Q
How is saliva regulated?
A
- PS: Ach –> IPs, Ca –> increases saliva
- S: NE –> cAMP –> increases saliva
20
Q
How is gastric acid secretion regulated?
A
- increased H+ secretion (when parietal cells open)
- -> vagus –> ACh –> IPs/Ca –> inc H+
–> G cells –> gastrin –> IP3/Ca –> inc H+
–> ECL cells –> histamine –> cAMP –> inc H+
*** decreased H+ secretion d/t GI cells (somatostatin –> dec cAMP) or gastric mucosa (–> prostaglandins –> dec cAMP)
21
Q
What controls bile secretions?
A
controlled by gallbladder contraction:
- CCK stims GB contraction (ACh release)
- ACh causes NO/VIP release –> acts on Sphincter of Oddi
22
Q
What’s the deal with carbs?
A
- only monosacchs are absorbed
- starch digestion d/t amylase (salivary glands/pancreas), sucrase, isomaltase (SI)
- glc actively absorbed with Na+ dependent transporter (luminal side) + GLUT2 (blood side)
23
Q
What’s the deal with proteins?
A
- only aas + di/tripeptides absorbed
- prots broken down by exopeptidase, endopeptidase, enterokinase, trypsinogen
- H+/peptide cotransport + basolateral aa transporter
24
Q
What’s the deal with lipids?
A
- digestion requires emulsification by bile salts –> form micelles (outside hydrophilic, inside hydrophobic_
- lingual + gastric lipases break into glycerol + FAs
- slow gastric emptying aids in lipid digestion (CCK slows in response to lipids + stims bile rls from GB)
- broken down to go into cell –> re-esterified in cell (chylomicrons)
25
How are fat-soluble vitamins absorbed?
- A, D, E, K
| - turn into micelles w/fat --> incorporated into chylomicrons
26
How are water-soluble vitamins absorbed?
- Vit B12 (absorbed in ileum via IF)
| - Na-dependent co-transport
27
How is iron absorbed?
- body content regulated by rate of intestinal absorption in duodenum
- delivered from heme or as ferric iron via GI lumen
- transported/stored bound to proteins
28
What is the SRY?
- sex-determining region of Y chromosome
- alters transcription for genes
- Anti-Mullerian Hormone (AMH - growth factor) prevents formation of mullarian ducts (via apoptosis)
29
How is gender differentiated?
Indifferentiated gonhad
--> + SRY --> testes --> Sertoli Cells (AMH) + Leydig Cells (testosterone) --> male genital tract + external genitalia
--> - SRY --> ovaries --> - AMH + - testosterone --> female genital tract + external genitalia
30
What are some sex chromosomal abnormalities?
- XO: gonadal dysgenesis/Turner's --> no sexual maturation, female external genitalia + phenotype
- XXX: superfemale
- YO: not compatible with life (no X)
- XXY: Kleinfelters --> small testes, reduced fertility, gynecomastia, behavioral deficits (born male but w/2º female sex characteristics)
31
What happens from in utero exposure of XX fetus to androgens?
- female pseudohermaphroditism
- typically male gender identity
- hormonal, not chromosomal
32
What happens in androgen resistance of XY fetus?
- male pseudohermaphroditism
- testicular feminization
- typically female gender identity
- congenital 5alpha-hydroxylase deficiency; congenital adrenal hyperplasia
33
What causes hypogonadism?
- impaired gonadotropin secretion --> decreased testosterone
- loss of T before puberty --> feminine characteristics, gynecomastia
- loss of T after puberty --> loss of libido
34
What form of testosterone may be used in the body?
- must be converted to estradiol via aromatase
- only free T is active
- most is bound in circulation to sex hormone binding globulin or ABP (androgen binding protein) in testes
- testosterone levels remain low until activation by pituitary gonadotropins in puberty
- testosterone stims sertoli cells to release inhibins (inh pituitary FSH biosyn + rls)
- inhibits GnRH release (after conversion to estradiol) + LH biosynthesis + release
35
What is GnRH? (in men)
- gonadotropin releasing hormone
- definition of puberty
- release is stimulated by NE, neuropeptide Y, leptin
- inhibited by melatonin, IL-1, DA, GABA, testosterone
- puberty initiated by pulsatile secretions of GnRH
36
What is LH? (in men)
stimulates T synthesis + release from Leydig cells in response to GnRH from hypothalamus)
37
What is FSH? (in men)
stimulates release of Androgen Binding Protein + inhibin from Sertoli Cells
38
What is inhibin?
inhibits pituitary production + release of FSH (made by Sertoli Cells)
39
What is Activin?
enhance RSH synthesis + secretion by blocking inhibin
inhibits inhibins har har har
40
Where is DHEA synthesized?
adrenal glands
41
Where is Androstenedione synthesized?
adrenal glands, gonads
42
Where is testosterone synthesized?
Leydig cells/testes
43
What are the three functions of testosterone and how are they carried out?
- Activates androgen receptor (internal genitalia, skeletal muscle, erythropoiesis)
- Conversion to DHT via 5alpha-reductase (external genitalia, hair, prostate growth)
- Conversion to estradiol (actual T effects): bone, libido
44
What is 17 hydroxysteroid DH?
key enzyme (last step) of testosterone synthesis
45
What is 5alpha-reductase?
- converts T to DHT (more potent androgen than T)
46
What is aromatase?
- converts T into estradiol (mostly produced in fat)
- -> estradiol mediates brain feedback on GnRH production + plays a role in epiphyseal closure/bone strength (if unresponsive to estradiol --> continued bone growth, osteoporosis)
47
What are the anabolic effects of androgens?
- increased protein synthesis
- block cortisol actions in breaking down proteins
- retention of Na, K, H2O, Ca, SO4, PO4
- increased kidney size
***cannot separate androgenic (virilizing) effects from anabolic effects
48
What are some of the bad effects of synthetic androgen abuse?
- gynecomastia
- liver damage (cholestasis, hepatitis, hepatic cysts)
- hepatocellular cancer
- suppression of gonadal fcn
- decreased T, sperm production, testicular size
- prostatic hyperplasia
- behavioral effects (dependence, aggressiveness)
49
What happens to male sexual characteristics with age?
- decreased testosterone (40yo)
- decreased sperm production (50yo)
- increased SHBG
- decreased E, libido, erectile capacity, muscle mess, cognitive fcn....AND SO MUCH MORE
50
What are the stages in ovarian follicle development?
1st stage: primordial follicle develops into a primary follicle (occurs w/conversion of oogonia to primary oocytes) --> arrested at this stage until puberty
2nd stage: takes place over 70-85d; only occurs during reproductive period (oocytes grow + mature)
3rd stage: one follicle becomes dominant (ova) over other follicles (15/28th day --> ovulation --> dominant follicle ruptures --> rls oocyte into peritoneal cavity)
51
What's the deal with oogenesis?
- primordial germ cells (mitotic division until gestational wk 20-24)
- primary oocytes: completed 6m after birth
- oocytes decrease with age until menopause (all gone)
52
What is the corpus luteum?
- formed by residual elements of ruptured follicle
- if fertilization occurs --> continues hormone secretion until placenta takes over
- if fertilization doesn't occur --> regresses during next 14d --> corpus albicans scar
53
What are theca cells?
- in the ovary
- synthesize + secrete progresterone
- express 17ß hydroxysteroid DH
- synthesize + secrete testosterone
54
What are granulosa cells?
- express aromatase
| - convert T to estradiol
55
What does GnRH do in women?
- intermittent, pulsatile release important to follicular phase (frequent, small pulses; estrogen increases frequency) and luteal phase (larger, less freq pulses; progesterone decreases frequency)
- leads to synthesis + rls of LH and FSH
56
What does FSH do in women?
- stimulates growth of developing follicles
- induces expression of LH receptors on theca + granulosa cells
- regulates activity of aromatase (stims estradiol prdcn)
57
What does LH do in women?
- acts on theca cells to stim synthesis of androstenedione + T
- required for rupture of dominant follicle
- induces expression of FSH receptor on granulosa cells
58
What are the three stages of the menstrual cycle?
- follicular phase: build-up of endometrium tissue (dominant hormone is estrogen)
- ovulation: estradiol levels rise sharply (LH dominant)
- luteal phase: endometrium fully developed to receive fertilized embryo (progesterone dominant)
59
What's so great about estrogen?
- maturation + maintenance of uterus, fallopian tubes, cervix, and vagina
- puberty (2º sex characteristics)
- blocks prolactin in breast/inh milk production
- maintenance of bone mast (decrease osteoclasts a lot, increase osteoblasts a little)
- proliferation of granulosa cells
- neg + pos feedback regulation of FSH + LH
60
What's so great about progesterone?
- maintenance of secretory activity of uterus during luteal phase
- neg feedback of FSH + LH
- important for maintenance of pregnancy
- stimulates transient breast epithelial proliferation
- increases body temp
61
What's the deal with estrogen receptors?
There are two:
- ER alpha (reproductive tract, lung, brain, vasculature) and beta (prostate, ovaries)
- products of separate genes but have 44% of the same aas
- shape determines function (bindings changes shape --> allows for dimerization --> attracts other proteins --> gets shit done)
62
What changes occur during puberty in females?
- it's the only period in your life you want to shop at abercrombie and fitch (dark times)
- first sign: breast budding (estrogen), then pubic hair
- menarche (many of 1st cycles are anovulatory)
63
What changes occur during menopause?
- preceded by anovulatory cycles (decrease number of functioning follicles)
- estrogen levels decrease
- LH, FSH increase
- thinning of vaginal epithelium + decrease in vaginal secretions
- increased bone loss
- decreased breast mass
- vascular instability (hot flashes)
64
When does fertilization occur?
- w/in 24 hours of ovulation
| - ovum begin to divide
65
When does implantation occur?
- after 5 days
- stuff happens
- meh
66
What hormones are involved in parturition?
- bunches
- physical: distension increases contractility
- estrogen/progresterone ration increases --> increase uterine sensitivity to contractile stimuli
- prostaglandins increase uterine contractility + softening/thinning of cervix
- oxytocin can stimulate uterine contraction + distension of cervix
67
What roles do estrogen + progesterone play during pregnancy + lactation?
- both: stimulate G&D of breast, block action of prolactin
--> at birth, decrease E/P levels --> relieve inhibition of prolactin on breasts
68
What role does oxytocin have on lactation?
- suckling stimulates oxytocin release --> contraction of myoepithelial cells --> milk ejection
69
What role does prolactin have on lactation?
- stimulated by sucking, TRH
| - prolactin at higher levels (lactation) inhibits GnRH release --> decreased fertility while breastfeeding
