Digestive 34 Flashcards
Mucus coated epithelium lines
Every surface facing the lumen. The mucus helps protect the wall of the tube and allows diffusion across the boundary.
Digestive tract function
Storage, transport, breaking down, absorbing nutrients, waste removal
Mouth
Humans are heterodonts, specialized teeth for different actions.
Homodonts teeth are all the same. Most reptiles, fish, and amphibians.
Crown
Visible part of the tooth
Periodontal ligament
Connective tissue rich in collagen that connects the cementum and alveolar bone of the tooth socket.
Von Ebner’s glands
Exocrine glands in the tongue that secret salivary lipase beginning the process of lipid hydrolysis.
Salivary glands
Parotid: Largest of the glands (mump, viral infection happens here)
Submandibular: produces 70% of saliva
Sublingual: produces mainly mucous
pH of saliva
7.2
Deglutition
Swallow
Saliva contains antibacterial agents
IgA: large protein that works with the immune system
Lysozyme: attacks cell wall of many gram positive bacteria
Lactoferrin: innate defense, antibacterial, antiviral, anti parasitic
Esophagus
Muscular tube that transports food from the mouth to the stomach. The esphoagela mucuosa is composed of stratified squamous epithelium.
Cardiac sphincter
Prevents backflow of the stomach contents into the esophagus.
Chyme
Thick acidic digestive fluid of ingested food.
pH of stomach is
- 5.
1) Destroy pathogens
2) Break down proteins - pepsin (protease)
Pepsinogen is released by
Chief cells.
It is a proenzyme or zymogen.
Cells that make HCl
Parietal cells
Cleavage
One of the ways to activate an enzyme. Removal of an aa allows for the needed conformation change to activate the enzyme. Both HCl and pepsin therefore are involved in this + feedback.
Gastrin
Peptide hormone that stim the secretion of HCl by parietal cells.
Gastrin is made by
G cells of the duodenum of the small intestine as well as cells in the stomach pylorus.
Parietal Cells
Produce HCl and Gastric Intrinsic Factor: a glycoprotein involved with a vitamin B12 absorption.
What is an ulcer?
Damage to epithelial layer. Substances such as aspirin and micro organism H pylori can lead to ulceration.
Stomach hormones (not exclusive)
Glucagon (enteroglucagon), somatostatin, serotonin, substance P, histamine, gastrin.
Small intestine
Largest % of digestion (macromolecule hydrolysis).
Duodenum, jejunum, ileum.
Duodenum
Carbohydrates, proteins, and fats are not totally digested yet.
Two ducts: Common bile and pancreatic ducts.
Duodenal hormones
Gastrin: Triggers secretion of HCl by parietal cells. Parietal cells have receptors for gastrin, histamine, and acetylcholine. Binding of these receptors cause the production and release of HCl.
Secretin: stimulates HCO3- release from pancreatic fluid.
Cholecystokinin: stims gall bladder contraction
VIP and Peristalsis
Vasoactive intestinal peptide are made by the duodenum. VIP increase peristalsis. Waves of contraction and relaxation in the smooth muscle lining the GI tract.
Lacteal in villus
Small intestine have villi, on villi are microvilli. Each villius contains a lacteal. Chylomicrons are transported to the lacteal and to the lymphatic system.
Chylomicrons
Fats coated with proteins, cholesterol, and phospholipids.
Villi blood pathway to Organs
From the villi, nutrient rich blood enters the hepatic portal vein and then to the liver.
Crypts
Between villi are invagination called crypts. Crypts are glands. Crypts of leiberkuhn contain goblet cells, enteroendocrine cells, and regen cells. Paneth cells make lysoszyme.
Peyer’s Patches
Aggregation of lymphoid tissue in the ileum wall. (Villi are the sparest here).
Monitor intestinal bacteria and prevent the growth of pathogenic bacteria.
Macrophages, dendritic cells, B lymph and T lymph.
Part of GALT, gut associated lymphoid tissue.
Jejunum
Villi also here but longer. Paneth cells within crypts of Lieberkuhn. No clear demarcation between the jejunum and ileum.
Ileum
Aa, bile salts, Vit B12 absorption occurs here. Peyer’s patches are here. Ileocecal valve.
Pancreas
Endocrine and Exocrine functions (Dual organ).
Endocrine: Insulin, glucagon, somatostatin (inhibits insulin and glucagon secretion).
Exocrine: Islets of langerhans.
2L of pancreatic juice/day
HCO3-, proteases (trypsin, chrmotrypsin, procarboxoypeptidase), amylases, lipases, nucleases, elastase.
Proteases
Trypsin and chymotrypsin are stored as zymogens. Cleaved and activated by enterokinase in the intestine.
Enterokinase is made by
Brunner glands of the duodenum
Trypsin can now activate other zymogens by
Proteolytic cleavages. Covalent modifications.
Pancreatic secretion is under the control of two hormones
CCK (cholecystokinin) and Secretin.
Acid and chyme enter the duodenum and stim the release of CCK and secretin.
Secretin
Makes the pancreatic juice alkaline.
Pepsin, amylase and trypsin optimal pH
2, 7, 8
Gall bladder
Store and concentrate Bile. Bile enters the duodenum via the common bile duct. 70mL of bile.
What triggers the release of bile?
CCK, acetylcholine from the vagus nerve.
Cholelithiasis
Gallstones. 80% of their composition is cholesterol. Liver is the culprit for the birth of gallstones.
Liver
Largest internal organ. Can regen. Hepatocytes divide in response to toxic substances. Compensatory hyperplasia. Hepatocytes liver about 150 days.
Glisson’s capsule
Surrounds the liver, layer of connective tissue.
Liver function
1) Make bile and cholesterol
2) Drug detox
3) Produce plasma proteins (albumin, fibrinogen)
4) Vitamin and Fe Storage (Vit A in greatest amount)
5) Deamination of proteins
6) chylomicrons are broken down -> glycerol and fatty acids
7) Makes 90% of blood proteins
8) Stores glycogen and releases
9) Urea production NH3-> urea.
10) Disposing of RBC
Bile characteristics
Emulsifer of lipids, not an enzyme, contain cholesterol, bile salts, bilirubin, phospholipids, water and IgA.
Bilirubin
Yellow green pigment that’s form when RBC are destroyed. Bilirubin is released into the bloodstream and is bound to albumin.
When circulating bilirubin levels are high in the blood during liver disease, yellowish discoloration of the skin occurs Jaundice.
Macrophages in the spleen and liver
In liver macrophages are called Kupffer cells.
What can cause jaundice?
Hepatitis, Increase hemolysis of RBC.
Liver Blood supply
a) Hepatic portal vein: Brings blood to the liver from the villi
b) Hepatic vein: transports deoxygenated blood away from the liver to the inferior vena cava.
c) Hepatic artery: carries oxygenated blood to the liver
Gluconeogenesis
Converting lipids and aa into glucose.
Hepatocytes
Large polyhedral cells, 6 or more sides. Hepatocytes have two or more nuclei. 50% are polyploid with 4,8,16 times the haploid chromosome complement.
Cirrhosis
Fibrous tissue replaces the normal hepatic architecture.
Portal triad
Portal Vein, hepatic artery, bile duct
Large intestine (Colon)
Stores waste, absorbs H20, produces mucus, Absorbs Vit K.
Cecum, Ascending, transverse, descending, sigmoid, rectum.
No villi
Appendix
No digestive function but part of MALT (mucosa associated lymphoid tissue). Immune function during early years of life. Aids in maturation of B lymphocytes and production of antibodies.
99% of the bacterial species residing ht ein large intestine are
obligate anaerobic bacteria.
Feces is
3/4 H2O and 1/4 solid matter with bacteria.
Small and large intestine absorbs __% of the H20
90% of the H20 that enters the GI tract.
Ruminants (cow or goat that can digest cellulose) guts
Ruminant bacteria are obligate anaerobic in nature