Flashcards in Exam 4: Digestive System Deck (58):
1
Gastrointestinal (GI) Tract
-tube that extends from mouth to anus
-mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus
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Functions of GI Tract
-digestion
-absorption
-elimination of wastes
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Digestion
-process of breaking down food into small fragments
-2 types mechanical and chemical
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Mechanical Digestion
-using forces/physically breaking down food
-Ex: stomach mechanically digests by muscle contraction
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Chemical Digestion
-uses enzymes (proteins) that speed up a chemical reaction
-Ex: stomach chemically digests with gastric juices
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Absorption
-water and food molecules pass through to GI lymphatics and blood vessels
-most nutrients absorbed in blood vessels
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Lacteals
-absorb lipids and lipid soluble vitamins in small intestine (A, D, E, K)
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Accessory Digestive Organs
-not part of GI tract but assist with digestion
-tongue, teeth, salivary glans, liver, gallbladder, pancreas
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Peritoneum
-serous membrane that lines the abdominal cavity
-parietal lines abdominal wall
-visceral covers abdominal organs
-peritoneal cavity is the space between the two, serous fluid secreted here
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Parasympathetic Innervation
-in general, it stimulates or increases activity of GI tract
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Sympathetic Innervation
-in general, it inhibits or decreases activity of GI tract
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Oral Cavity
-continuous posteriorly with oropharynx
-nonkeratinized stratified squamous epithelium
-upper part of the oral cavity: palate
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Hard Palate
-anterior 2/3 of palate, bony
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Soft Palate
-posterior 1/3 of palate, formed from skeletal muscle
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Uvula
-dangling muscle off soft palate
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Extra Credit Names
-Osmosis Jones and Drix
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Function of Soft Palate and Uvula
-close off opening to nasopharynx when you swallow
-these muscles move and that's why milk goes up your nose
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Teeth
-20 deciduous (baby) teeth replaced by 32 permanent teeth
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Tongue
-big skeletal muscle
-covered with stratified squamous epithelium
-function: perceives taste and mechanical digestion
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Salivary Glands
-3 pairs
-secrete saliva composed of water, mucus, amylase (digests carbs), lysozyme (antibacterial agent) and antibodies
-functions: dissolves food molecules so they can be tasted, moistens food and turns it into bolus, chemically digests carbs, cleanses mouth, lysozyme and antibodies inhibit bacterial growth
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Pharynx
-throat
-muscular tube that connects nasal cavity and mouth, to larynx and esophagus
-function: propel food and drink to esophagus and air to larynx
-only the oropharynx and laryngopharynx conduct both food and air
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GI Tract Layers
-4 layers, tunics
-mucosa, submucosa, muscularis, adventita/serosa
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Mucuosa
-innermost tunic
-esophagus has nonkeratinized stratified squamous epithelium
-stomach to anal canal has simple columnar epithelium
-areolar CT
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Muscularis Mucosae
-thin layer of smooth muscle
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Submucosa
-connective tissue
-contains major blood vessels
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Muscularis
-typically contains 2 layers of smooth muscle:
-exception: stomach (3 layers)
-inner circular layer
-outer longitudinal layer
-responsible for peristalsis: alternate waves of contraction and relaxation
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Serosa or Adventitia
- outermost layer
-serosa = visceral peritoneum + areolar CT
-adventitia = areolar CT only
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Esophagus Gross Anatomy
-muscular tube that connects pharynx to stomach
-function:propel food to stomach
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Esophagus Histology
-mucosa: nonkeratinized stratified squamous epithelium
-muscularis: 2 layers of muscle
-upper 1/3: skeletal muscle
-middle 1/3: skeletal + smooth
-lower 1/3: smooth muscle only
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Reflux Esophagitis
-heartburn
-stomach contents back flow (reflux) into esophagus causing burning pain
-risk factors: overweight, smoking, large meals before bedtime
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Stomach Gross Anatomy
-connects to esophagus and duodenum
-upper left quadrant
-main function: uses mechanical and chemical digestion to turn bolus into chyme
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Stomach Histology
-mucosa has simple columnar epithelium
-mucosa contains gastric pits
-branching off of gastric pits are gastric glands
- muscularis: has three (3) layers of smooth muscle: innermost oblique, inner circular, outer longitudinal
-3 layers blend bolus with gastric juice turning the bolus into chyme
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Gastric Glands
-cells that secrete gastric juice (acidic, contains HCl)
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What prevents gastric juices from eating away at stomach itself?
-cells secrete layer of mucus-protective lining
-epithelium constantly regenerating
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Peptic Ulcer
-erosion of wall of stomach or duodenum
-"balance" between acidic juices and mucosa repair thrown off so acid eats away at lining
-most causes are due to infection (helicobacter pylori)
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Small Intestine Gross Anatomy
-functions: finishes chemical digestion process
-absorbs most (90%) of nutrients
-3 specific segments
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Duodenum
-connects to stomach
-receives chyme from stomach
-receives bile and pancreatic enzymes through duodenal papilla
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Jejunum
-middle part
-connects to duodenum and ileum
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Ileum
-connects to cecum of large intestine
-majority of last part of chemicals get secreted and interact with chyme
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Small Intestine Histology
-mucosa has simple columnar epithelium w/ goblet cells
-small intestine contains circular folds (plicae circulares): folds of mucosa AND submucosa!
-functions: act like speed bumps to slow down chyme, increase surface area for absorption
-on circular folds are villi
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Villi
-folds of the MUCOSA only!
-function: increase surface area
-in center of each villus are blood vessels and a lacteal
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Lacteal
-lymphatic capillary
-absorbs lipids and lipid soluble vitamins (A, D, E, K)
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Large Intestine Gross Anatomy
-functions: most absorption of water and electrolytes (Na+, K+) and stores feces until they can be expelled from body
-different segments: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum and anal canal
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Cecum
-sac that connects to ileum
-lower right part of abdomen
-vermiform appendix attaches here
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Rectum and Anal Canal
-terminal portion of large intestine
-feces leaves anal canal through anus
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Large Intestine Histology
- mucosa has simple columnar epithelium w/ goblet cells
-muscularis: 2 layers of smooth muscle: outer longitudinal layer consists of teniae coli
-haustra
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Teniae Coli
-3 thin bands of smooth muscle that bunch large intestine into sacs called haustra
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Colorectal Cancer
-most arise from polyps from mucosa
-not all polyps are cancerous
-blood in stool early warning sign
-colonoscopy to examine colon
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Liver
-upper right part of abdomen
-functions: produce and secrete bile, processes products of digestion
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Gallbladder
-underneath liver
-function: stores and concentrates bile
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Gallstones
-condensations of bile material into stones
-first form in gallbladder
-painful if travel through billary apparatus
-4 F's risk factors: female, fat, fertile (had at least one child), forty's (or older)
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Pancreas
-behind stomach
-acinar cells
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Acinar Cells
-secreate pancreatic juice: contains digestive enzymes, alkaline, neutralizes acidic chyme
-pancreatic juice leaves via a pancreatic duct
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Billary Apparatus
-a network of "tubes" that transport bile and pancreatic juices TO the duodenum!
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Arterial Blood Supply to Abdominal GI Tract
-from branches of:
1) celiac trunk
2) superior mesenteric artery
3) inferior mesenteric artery
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Venous Drainage of Blood from Abdominal GI Tract
-hepatic portal system: veins that drain blood from GI tract directly to liver, transports blood low in oxygen but high in nutrients to be processed
-4 mein veins.
1. Superior Mesenteric vein
2. Splenic vein
3. Inferior Mesenteric vein
4. Hepatic portal vein - receives blood from 1,2, and 3, and goes directly to the liver
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Blood from Hepatic Portal vein
-processed by liver cells (hepatocytes)
-also get oxygenated blood from hepatic arteries
-once processed, blood leaves the liver via hepatic veins and into the inferior vena cava
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