o Duodenum o Jejunum o Ileum o Circular folds – force chyme to slowly spiral through luen o Villi – fingerlike extensions of the mucosa o Microvilli – contains brush border enzymes Define propulsion, retropulsion, and grinding Hormones from duodenum o Secretin – regulates pH o Cholecystokinin (CCK) – causes the release of bile from the gall bladder Liver o Largest gland in the body o Four lobes – right, left caudate, and quadrate Falciform Ligament o Separates the (larger) right and (smaller) left lobes o Suspends liver from the diaphragm and anterior abdominal wall Bile o Produced by liver and stored in gall bladder o Yellow-green, alkaline solution: Emulsifies fats Gallbladder o Thin-walled muscular sac o Stores and concentrates bile by absorbing its water and ions o Releases bile via the cystic duct, which flows into the bile duct Pancreas o Deep to the greater curvature of the stomach o Head in encircled by the duodenum, tail near the spleen Histology of the Pancreas o Exocrine functions: 99% exocrine clusters Secrete pancreatic juice Fluid and enzymes o Endocrine functions 10
Anatomy II Biology 2130k Hormones: glucagon and insulin 11
Pancreatic juice o Watery alkaline solution (ph 8)neutralizes chyme o Many enzymes: 1. Pancreatic amylase – CHO breakdown 2. Trypsin – protein breakdown 3. Pancreatic lipase – fat breakdown Motility of the small intestine o Peristalsis Each wave starts distal to the previous (the migrating motility complex) Meal remnants, bacteria, and debris are moved to the large intestine Large intestine o Regions Cecum (pouch with attached appendix) Colon – ascending, transverse, descending, sigmoid Rectum Anal canal o Ileocecal sphincter (valve) Allows passage into large intestine o Unique features: Teniae coli Three bands of longitudinal smooth muscle in the muscularis Haustra Pocketlike sacs; segmental movement Epiploic appendages Fat-filled pouches of visceral peritoneum Functions of the large intestine o Vitamins, water, and electrolytes are reclaimed o Major function is propulsion of the feces toward the anus o Colon is not essential for life Motility of the large intestine o Gastrocolic reflex Initiated by presence of food in the stomach Activates three to four slow powerful peristaltic waves per day in the colon (mess movement) Colon o Mesenteries – double layer of membranous tissue connecting various parts of the abdominal cavity Rectum and anus o Rectum 12
Anatomy II Biology 2130k Three rectal valves stop feces o Anal canal The last segment of the large intestine o Sphincters Internal anal sphincter – smooth muscle External anal sphincter – skeletal muscle Defecation o Mass movements force feces into rectum o Parasympathetic signals Stimulate contraction of the sigmoid colon and rectum Relax the internal anal sphincter o Conscious control allows relaxation of external anal sphincter Chemical Digestion o Catabolic o Enzymatic o hydrolysis 13
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