Exam 4 Flashcards
What compose the walls of the large intestine?
The walls are thinner that the small intestine and have no villi
Goblet cells: secrete mucus for lubrication
Distinctive intestinal crypts: dips of simple columnar cells - contain goblet cells: lubricate undigested material, contain large lymphoid nodules (part of GALT)
What part of digestion does the large intestine play?
Some nutrient absorption, mostly absorbs water from chyme.
Mostly bacteria digestion
What is the “bacteria digestion” in the large intestine?
The microbiome (all non-human cells in/on body) majorly E. Coli breaks down the undigested (body just didn’t absorb) carbs, proteins, and lipids & converts vitamins into absorbable versions (ie vitamin K)
What is the membrane of the digestive system and what are its parts?
Peritoneum: serous membrane of the abdominal cavity
-Visceral: covering most digestive organs
-Parietal: line abdominal cavity wall
-Peritoneal cavity: fluid-filled space to lubricate the organs
What is mesentery and what is its function?
A special peritoneum: a double layer of visceral peritoneum stuck together with areolar connective tissue in between.
Function: stabilize organ, blood vessel, and nerve positions
What are the three types of mesentery?
1) Mesentery proper: supporting the small intestine (attached to jejunum)
2) Greater omentum: peritoneum plus adipose that hangs off the greater curvature of the stomach to the inferior organs (intestines)
3) Lesser omentum: peritoneum plus adipose tissue hangs off lesser curvature of stomach to superior organs (liver)
What are the layers of the digestive tube deep to superficial?
Mucosa, submucosa, muscularis, serosa (visceral peritoneum)
then the mesentery
What comprises the mucosa?
Epithelial tissue: contact with lumen
-non-keratinized stratified squamous in oral cavity, pharynx, esophagus, anus (close to external environment)
-simple columnar: rest of digestive system
Connective tissue:
-lamina propria: supporting ET in mucus membranes (supports villi),
-areolar CT, capillaries, nervous tissue, and lymphatic vessels
Muscularis mucosae: smooth muscle supporting mucosa
What comprises the submucosa?
(Not a mucus membrane, but goes into plica)
Dense irregular connective tissue
Large blood vessels, lymphatic vessels, and glands
What comprises the muscularis externa and what is its function?
(it is a big layer of muscle)
Circular- like a ring, and longitudinal (running length of tube) smooth muscle layers
Function: peristalsis- longitudinal, but also circular and segmentation- mostly circular
What comprises the serosa and where is it found?
Visceral layer of serous membrane
Located: everywhere but pharynx, esophagus, and rectum which has adventitia
What is the cephalic phase of digestion and what occurs in it?
The first phase: digesting lipids and carbs with chemical and mechanical digestion. Also provides for defense
What is the chemical digestion of the cephalic phase?
Saliva:
-softens & lubricates food (b/c mostly water)
-salivary amylase (enzyme),
-dissolves food (allows for tastents to be detected by taste buds)
Lingual Lipase:
-breaks down fats mainly triglycerides
What is the mechanical digestion and defense of the cephalic phase?
Mechanical digestion:
- mastication, “chewing” of pre-molars and molars
Defense:
-lysozyme and immunoglobins destroy/disable certain bacteria and viruses on/in the food we eat
What is the gastric phase of digestion and what occurs in it?
The second phase of digestion, digesting lipids and proteins
The stomach contains cells that are involved in chemical digestion and cells that are involved in protection (keeping the other secretions at a pH of 2 from digesting the stomach wall)
Mucus, G, Parietal, Chief, ECL, and D cells
What do the mucus cells of the stomach do?
Produce mucus and bicarbonate for protection
-mucus: physical barrier between lumen and epithelium -bicarbonate: buffers gastric acid to pH ~7 directly over cells to prevent damage to epithelium
What do the G cells of the stomach do?
Secrete gastrin that tells another group of cells (parietal cells) in the stomach to secrete gastric acid
What do the Parietal cells of the stomach do?
Secretes
-Gastric acid (HCl) that kills microbes in the digestive track, activate pepsin (from pepsinogen for chemical digestion- break peptide chains into smaller fragments), denatures proteins (for easier digestion), stimulate somatostatin release (from D cells), stop activity of salivary amylase (no carb digestion)
-Intrinsic Factor: bind to B12 allow for absorption
What do the chief cells of the stomach do?
Secrete:
-Pepsinogen: inactive form of pepsin that will
-Gastric lipase: digest lipids
What do the ECL cells of the stomach do?
Secrete histamine to act on parietal cells for the simulation of gastric acid secretion
What do the D cells of the stomach do?
Release somatostatin that will inhibit G, Chief, and ECL cells (inhibit gastric acid and histamine secretion)
What is the intestinal phase of digestion and what occurs in it?
Third phase of digestion,
Digestion of proteins, lipids, carbs, & nucleic acid. Chemical digestion
Secretions from small intestine, pancreas, and liver
What are the secretions of the small intestine?
Goblet cells, Crypt Cells, and Brush-boarder enzymes.
What are the secretions of the pancreas?
Bicarbonate: buffer pH from 2 to 7
Pancreatic amylase: digest starch
Pancreatic lipase: digest lipids
Pancreatic proteases: digest protein (hard to digest)
Pancreatic nuclease: digest nucleic acids
What are the pancreatic proteases?
Inactive: Trypsinogen, chymotrypsinogen, and procarboxypeptidase
Trypsinogen activated to trypsin by specific brush boarder: protease enteropeptidase
Trypsin activates chymotrypsinogen to chymotrypsin and procarboxypeptidase to carboxypeptidase
Once activated they can digest proteins
What are the secretions of the liver and what do they do?
Bile salts to duodenum to emulsify fats turning fat globule to fat droplets and recycled by liver
They do not break down triglycerides
What do the Goblet cells of the small intestine do?
Goblet cells: mucus for lubrication for easy movement
What do the crypt cells of the small intestine do?
Crypt Cells: isotone saline solution: NaCl offering a slippery environment for softening and dissolving
What are the brush boarder enzymes of the small intestine and what do they do?
They are embedded in plasma membrane of villi
They provide last point of contact for nutrient digestion (carbs, proteins, nucleic acid)
They transport from lumen to cell to blood vessel after nutrients are broken to small segments:
(Carbs to monosaccharides, proteins to amino acids or peptides, nucleic acids to nitrogenous bases and monosaccharides)
How is the pancreas involved in lipid digestion?
Pancreatic lipase binds with colipase (also from pancreas) that displaces bile salts (detaches them from the fat droplet) so that the lipase can stick to the triglycerides and break off two fatty acids.
What happens to the remnants of the triglycerides?
Some of the fatty acids and the monoglyceride are absorbed into the epithelium while other form micelles–rings of fatty acids and monoglycerides that move down the digestive tract and are absorbed along the way
How do the epithelial cells absorb lipids and what happens next?
Fatty acids and monoglycerides enter cells via simple diffusion. Endoplasmic reticulum reassembles triglycerides (too big fit through). Golgi apparatus assembles triglycerides into chylomicrons.
What are chylomicrons and what happens to them?
Chylomicrons are triglycerides plus a protein to make them water-soluble (transportable by lymph & plasma). Chylomicrons excreted via exocytosis into interstitial fluid (opposite of lumen) and enter lymphatic system via lacteals in plica and eventually to the blood stream (ducts –> subclavian veins)
What are testes and where are they located?
The male structures that produce sex cells (spermatozoa/sperm). Located external to body in pouches called scrotum because they must be below the core temperature.
What else are in the scrotum and what is their function?
Dartos & cremaster muscles: move position of scrotum closer/farther from pelvis to regulate the temperature of the testes.
What is the function of the inguinal canal?
It is the canal through which the testes descend during development. After this it contains the spermatic cord connecting the testes to the pelvic cavity containing the ductus deferens, the testicular artery and veins, and nerves
What are the two main structures in the testes and what are their general jobs?
The seminiferous tubules: very tiny tubes for sperm production
Interstitial cells: between the tubules to make testosterone
What are the layers of the seminiferous tubules? Superficial to deep
Spermatogonia (germ–stem–cells that produce sperm)
Primary spermatocyte
Secondary spermatocyte
Spermatids
Lumen (spermatozoa)