Unit 5 Flashcards
What are the 6 functions of the digestive system?
- Ingestion
- Digestion (mechanical and chemical)
- Secretion (mucus, HCl, enzymes, hormones)
- Movement (peristaltic movement of food through tract)
- Absorption
- Excretion
** Mnemonic: What month is it? “IDS MAE**”
What are the layers of the GI tract wall?
- Mucosa (inner epithelial layer)
- Submucosa (blood, lymph, nerves)
- Muscularis Externa (inner circular, outer longitudinal)
- Serosa (supportive outer CT)
Mnemonic: Ms. Mess (M, S, ME, S)
How is mechanical digestion performed?
by chewing and muscular contractions of the stomach/intestines
What is the term for smooth muscle movement of food through the digestive tract from the mouth to the anus?
Peristalsis
What are the two layers of the muscularis externa and how do they act on food/chyme within the GI tract?
Inner Circular - contracts/relaxes to tighten/loosen around chyme rhythmically moving food along the length of GI tract and also mixing chyme to increase enzyme action, etc.
Outer Longitudinal - contracts/relaxes to shorten/lengthen segments of tract, contributing to peristaltic movement along the tract
What special structures does the oral cavity contain and why?
What kind of secretions are released here and what is the pH?
Teeth & Tongue - mechanical digestion
Salivary Glands - moistening the bolus
Saliva is secreted which contains mucus, water, antibacterial enzymes and amylase, which starts starch breakdown and operates at the oral cavity pH of 6-7
What kind of cells line the oral cavity?
Why?
Stratified Squamous Epithelium
- undergoes fast mitosis to grow back and protect from food abrasion
What is the name of the passage between the oral cavity and stomach?
What cells line it?
How long is it?
What is special about its muscularis externa layer?
Esophagus
- simple squamous epithelium
- about b long
- Muscularis layer is top 1/3 skeletal, middle 1/3 mixed and bottom 1/3 smooth muscle for voluntary/involuntary control of swallowing
What kind of cells line the stomach?
What is its pH?
How is it able to hold a whole meal’s worth of food
What is special about its muscularis externa and why?
Simple Columnar Epithelium
pH 2
mucosal folds called rugae allow for expansion
Muscularis has inner oblique, middle circular and outer longitudinal layers for better churning of food and jacknife contractions to move chyme into the pyloric region and through the pyloric sphincter into the duodenum
What are the absorptive features of the small intestine?
And what is their function?
- Microvilli - cytoplasmic extensions of the apical end of epithelial cells
- Villi - larger folds in the mucosa itself
- Circular folds - “plicae circulares”, even larger folds in the submocsa
Increase the surface area of the GI tract.
What is the structure that separates the stomach from the small intestine?
And what specific parts of the stomach and small intestine does it separate/connect?
Pyloric Sphincter
** **controls passage of food from the pyloric region of the stomach to the duodenum of the SI
what is the enlarged portion of the stomach that extends slightly superior to and left of where the esophagus and stomach meet?
fundus
what is the structure that separates the stomach from the esophagus?
gastroesophageal sphincter
What are the 4 main types of cells in the gastric epithelium?
their major functions?
- **mucus cells - **secrete mucus
- chief cells - secrete pepsinogen (which becomes pepsin in HCl)
- parietal cells - secrete HCl
- enteroendocrine cells - secretes gastrin, increasing gastric activity
what is the name of the liquid slurry of food that has been chewed, churned and acidified by the stomach?
chyme
what kinds of cells line the small intestine?
simple columnar epithelium
What are the 3 sections of the small intestine and their approximate length and function?
- Duodenum - 1 foot, enzymatic action & digestion
- Jejunum - 8 feet, digestion & absorption
- Ileum - 12 feet, primarily absorption
What are the accessory organs of the digestive system?
Liver
Gallbladder
Pancreas
What is the digestive function of the liver and gallbladder?
the liver turns bilirubin into bile salts
** **the gallbladder stores and concentrates bile by reabsorbing some electrolytes and water from it
when a fatty meal is ingested, the gallbladder releases bile into the duodenum via the common bile duct
What are the two kinds of pancreatic function?
And the main action of each?
Exocrine - digestive enzyme (amylase, lipase, proteases) and sodium bicarbonate (NaHCO3) release into the duodenum via the pancreatic duct
**Endocrine - **cells of the islets of Langerhans secrete hormones to control blood sugar
- Beta cells secrete **insulin **to decrease blood glucose
- Alpha cells secrete glucagon to increase blood glucose
What are the two types of Diabetes Mellitus and their differences?
type 1 - auto-immune attack on Beta cells causes little to no creation/secretion of insulin, requires insulin supplementation
**type 2 - **also known as insulin resistance, caused by genetics and diet as a result of chronic blood sugar spiking and increased tolerance of cells to insulin, can be controlled by diet and exercise but sometimes requires supplemental insulin
What are the 3 phases of gastric secretion control?
- cephalic - thinking about food, causes gastrin release
- **gastric - **physical stretching of stomach causes gastrin and HCl release
- intestinal - duodenal feedback, slows gastric secretion to modulate entrance of chyme into SI
What 3 factors can cause gastric secretions to stop or decrease?
- lack of proteins present
- duodenal feedback
- somatostatin release (released by duodenum to slow gastric activity)
What are the 3 duodenal hormones that affect gastric activity?
What are their effects?
**Secretin - **water homeostasis (also slows HCl, increases HCO3-)
Cholecystokinin (CCK) - stimulates fat/protein digestion by signaling bile/enzyme release
**Somatostatin - **regulates insulin/glucagon
What factors affect duodenal activity?
- fat in chyme - slows duodenal digestion and gastric emptying
- hyertonicity of chyme - higher tonicity slows digestion
- acidity of chyme - higher acidity requires more neutralization/time
- distension of duodenum - more distension slows digestion time
How are proteins and carbs absorbed in the small intestine?
Proteins are broken into amino acids, carbs are broken into monosaccharides (mostly glucose and fructose)
AAs and Glucose undergo secondary active transport with Na+ from SI lumen into cells, then diffuse into blood from cells (Na+/K+ actively antiport into/out of blood)
Fructose undergoes uniport diffusion via a carrier protein
How are lipids absorbed in the small intestine?
Draw it.
lymphatically in several steps:
- SI lipase breaks triglyceride into glycerol + 3 FAs
- Glycerol and FAs combine with bile salts to form micelles, which are absorbed into intestinal epithelium
- Bile is reabsorbed into SI while glycerol and FAs reform triglycerides
- Triglycerides within epithelium are protein-coated to form chylomicrons, which are absorbed into lymph
In what 5 main ways do hormones alter cellular activity?
- increase/decrease rates of mitosis
- turn on or off enzymes
- make different proteins
- alter membrane permeability
- alter secretory activity
What are the 3 hormonal release mechanisms?
- Humoral - based on concentration of substances in blood (glucose levels rise, causing insulin release)
- Nervous - NS stimulates release of hormone from gland (sympathetic NS release of epinephrine from adrenal medulla)
- Hormonal - hormones from one gland stimulate release of hormones from another (tropic hormones of the anterior pituitary)
How do protein-based hormones act on cells?
Why?
Explain the process.
Draw it.
Secondary Messenger Activity
**- **because they are hydrophilic and can’t easily enter the cell
Process:
- hormone reacts with surface receptor on cell membrane
- receptor activates G-protein
- G-protein activates adenylate cyclase
- ad-cyc converts ATP to cyclic AMP which is secondary messenger
- cAMP activates protein kinases
All of this takes place on the cell membrane until the cAMP leaves the membrane to activate the protein kinases.
1.
What do protein kinases do?
- modifies proteins
- effects enzyme actions
- turns off enzymes
How do steroid hormones act on cells?
direct gene activation
Process:
- diffuses into cell membrane
- enters nucleus, combines with receptor
- hormone/receptor complex alters DNA
What endocrine organ is considered the main homeostatic organ of the body?
What does it lack that other structures around it have?
What two main hormones does it make?
hypothalamus
- lacks blood brain barrier
- makes oxytocin and ADH
What are the anterior pituitary hormones that act on other endocrine glands called?
Tropic Hormones:
- Thyroid Stimulating Hormone (TSH) - self explanatory
- Adrenocorticotropic Hormone (ACTH) - also self exp
- Luteinizing Hormone (LH) - stimulates ovulation/testosterone production
- Follicle-Stimulating Hormone (FSH) - regulates growth, development and pubertal maturation, stimulates ovarian follicle growth
LH and FSH are gonadotropins
What are the non-tropic hormones of the anterior pituitary?
- Growth Hormone - stimulates muscle/bone growth
- Prolactin - stimulates milk production
- Melanocyte-Stimulating Hormone - stimulates melanocytes to make melanin
What are the two types of cells in the thyroid?
What do they secrete?
What do their secretions do?
- Follicular Cells - use iodine, secrete T3 and T4 which make up T7, which regulates basal metabolic rate
- Parafollicular Cells - secrete **calcitonin, **which activates osteoblasts, building bone and lowering blood Ca levels
What does parathyroid hormone do?
Through what 3 mechanisms?
Raises blood Ca++ levels
by…
- activating osteoclasts
- increasing Ca++ absorption in intestines
- decreasing renal excretion of Ca++
What are the 3 types of adrenal cortex hormones?
Examples?
- **Mineralocorticoids **(Aldosterone)
- Glucocorticoids (cortisol, hydrocortisone)
- Gonadocorticoids (androgens)
What is the primary function of the ovaries?
What hormones act on it and what hormones does it create?
How is it also exocrine?
- production of primary follicle with oocyte
**- **acted on by LH and FSH
- creates estrogen and progesterone, which regulate ovarian cycle
- releases egg to fallopian tube in an exocrine fashion
What are the exocrine and endocrine functions of the testes?
exocrine - sperm cell production and secretion via meiosis
endocrine - testosterone production via interstitial cells
what are the unused byproducts of female meiosis that do not become mature oocytes called?
polar bodies
how much cooler than the body is the scrotum?
1-2 degrees Celsius
What is the route of sperm flow from testes to outside the body?
- seminiferous tubules
- epididymis
- vas deferens
- ejaculatory duct
- urethra
mnemonic: STEV DEDU
How long do sperm spend maturing in the epididymis?
20 days
What 3 glands release the constituents of ejaculate?
In what percentages?
And with what functions?
- seminal vesicle - 60% of fluid, alkaline and fructose-rich
- prostate - 30% of fluid, acidic w/ prostaglandins to reverse uterine peristalsis
- bulbourethral glands - 10% of fluids, alkaline to neutralize urinary acid in urethra
What are the 3 phases of the ovarian follicle?
primary
secondary
Graffian (mature)
What are the 3 phases of the ovarian cycle?
Their related hormone levels? And days?
- Follicular Phase (days 1-13) - primary follicle to mature follicle via FSH and LH
- Ovulation Phase (days 14-15) - mature follicle ruptures, releases egg via an estrogen spike
- Corpus Luteal Phase (days 16-30) - ruptured follicle becomes corpus luteum, releases progesterone
What are the 3 phases of the uterine cycle?
The activities during them? And hormones?
- Menses (days 1-7) - shedding of endometrium, drop in progesterone
- Proliferative (days 8-15) - enodometrium thickens, estrogen rises
- Secretory (days 16-30) - endometrium thickens further, progesterone is high
