The digestive system Flashcards
What are the four basic digestive processes?
Digestion
Absorption
Secretion
Motility
What are the two types of digestion?
Mechnaical digestion
Chemical digestion
Absorption
Passage of the end - products of chemcial digestion from the digestion tract into blood or lymph for distrubution to tissue cells
Secretion
Enzymes and digestive fluid secreted by the digestive tract and its accesory organs facilitate chemcial digestion
Elimnation
Undigested material will be release through the rectum and anus by defecation
features of the GI wall structure
Muscosa
Submucosa
Muscularis externa
Serosa
Mucosa
Lining of the lumen of the GI tract
3 layers - mucuous membrane, Lamina propria, muscualris mucosae
Submucosa
Contains connective tissue which adds to the elastcicity of the tact
Muscualris externa
Smooth msucle
Responisble for motility along the GI tract
Serosa
Continous with the messentery
Thick layer of connective tissue offers structural support of the tract
Palate - rood of the mouth
2 distnct pottion
Hard palate- anterior portion, tongue forces food againts it during chewing
Soft palatae - posterior portion, soft flap which blocks the nasopharynx during swallowing
The beginning - Mastication
Digestion begins with mastication
Salivary galnds - partoid gands, sublingual gland, submandibualr gland
Salivary amylase
catalyses the hydrolysis breakdown of polysaccharides like starch into smaller molecules
Beginning process of digestion
Pharynx
Food passes nasopharynx - closure by soft palate during swallowing
Upper esophgeal sphincter - protects against reflux of food into the airways
Stomach
Food passes through the cardiac sphincter into the stomach
Stomach lined with simle columnar epithelial cells
Parts of the stomach
Fundus - top part of the stomach
Body - large mid - protion of the stomach
Antrum - lower part of the stomach
Pyloric region - terminal region of the stomach
Pyloric sphincter - control entry of chyme into the small intestine
Acidic environemnt of stomach
pH = 2 Necessary for activating pepsingoen Denatures proteins Kills bacteria Gastric mucosal barrier
Gastric pits
Located in stomach lining; lead to gastric glands
Secretory products then Gastric pits
Pepsinggen - secreted by chief cells
HCI - secreted by pariteal cells
Intrinsic factor - secreted by parietreal cells
Gastrin - hormone secreted from enteroendocrine cells
Mucus - secreted from neck cells
Small Intestine
Coiled, hollow tube
Primary site of digestion and absorption
Lined with simple columnar epithelium
Three division - Duodenum, Jejunum and Ileum
Microvilli
Finger - like projections
Villi increase surfaces areas of epithelium
Form brush border
Crypts of Lieberkuhn
Present between villi
secreted in duodenum
Absorbed in ileum
Role of liver in absorption
Absorbed nutrients travel in blood to the liver before entering the general circulation
liver functions to detoxify substances and processes certain nutrients
Large Intestine
Consists of cecum, colon and rectum
Illececal sphincter is between ileum and colon
Teniae coil are bands of longitudinal smooth muscle
What are the four types of accesory glands?
Slaivary galnds - secrete saliva
Pancreas - secretes pancreatic juice
Liver - secretes bile
Gallbladder - stores bile produced by the liver
The pancreas
Has endocrine and exocrine pancreas
pancreas tissue consist of exocrine acinar cells and duct cells. Endocrine cells dispersed in the islets of Langerhans
Pancreatic juice contains -
Bicarbonate which neutralizes acidic pH of the stomach acid to pH 8.0
Pnacreatic amylase - hydrolyses carbohydrates like maltose to glucose molecules
lipases
Proteases
Nucleases
The liver
Secretes bile
Bile enter duodenum
Processes nutrients
Functions of the liver
Secretion and modification of hromones
Removal of old red blood cells
Synthesis of plasma proteins
Elimination of waster and toxins
The biliary system
Liver synthesizes bile Gallbladder stores bile Common bild duct transports bile from liver Joins with panvcreatic duct to form Spincter of Oddi
Carbohydrate digestion
Only monosaccharides are absorbed
Disaccharides and polysaccharides must be digested to monosaccharides
Digestion of starch
Enzymes of carbohydrate digestion
Dextrinase Salviary and pancreatic amylase Sucrase Lactase Maltase
Protein digestion
Amino acid
Dipeptides
Tripeptides
Types of protease used in the body to dugest protein
Endopeptidases
Exopeptides
Zymogens
Absoprtion of amino acids
Cross the apical membrane by sodium - linked secondary active transport or facilitated diffusion
Cross the basolateral membrane by facilitated diffusion
Lipid digestion
Lipids face special problm in digestion and absorption
Enzymes of digestion
Secreted from pancreas
Lipases can only act on molecules near the edge of a fat droplet
Bile salts
Synthesized in liver from cholesterol
Sceretd in bile to duodenum
Amphipathic molecule
Emulsify fat
Absorption of vitamins
Fat soluble vitamins
Vitamin B12
Water - soubule vitamins
Absorption of minerals
Sodium
Chloride
Potassium
Hormones involved of GI tract
Leptin
Gastrin
Secretin
CCK
Peristalisis
Seris of wave - like muscle contraction that move food through the digestive tract
Causes movement of the wall of the GI tract
