Exam 4: Digestive System Flashcards
Gastrointestinal (GI) Tract
- tube that extends from mouth to anus
- mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus
Functions of GI Tract
- digestion
- absorption
- elimination of wastes
Digestion
- process of breaking down food into small fragments
- 2 types mechanical and chemical
Mechanical Digestion
- using forces/physically breaking down food
- Ex: stomach mechanically digests by muscle contraction
Chemical Digestion
- uses enzymes (proteins) that speed up a chemical reaction
- Ex: stomach chemically digests with gastric juices
Absorption
- water and food molecules pass through to GI lymphatics and blood vessels
- most nutrients absorbed in blood vessels
Lacteals
-absorb lipids and lipid soluble vitamins in small intestine (A, D, E, K)
Accessory Digestive Organs
- not part of GI tract but assist with digestion
- tongue, teeth, salivary glans, liver, gallbladder, pancreas
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
Parasympathetic Innervation
-in general, it stimulates or increases activity of GI tract
Sympathetic Innervation
-in general, it inhibits or decreases activity of GI tract
Oral Cavity
- continuous posteriorly with oropharynx
- nonkeratinized stratified squamous epithelium
- upper part of the oral cavity: palate
Hard Palate
-anterior 2/3 of palate, bony
Soft Palate
-posterior 1/3 of palate, formed from skeletal muscle
Uvula
-dangling muscle off soft palate
Extra Credit Names
-Osmosis Jones and Drix
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
Teeth
-20 deciduous (baby) teeth replaced by 32 permanent teeth
Tongue
- big skeletal muscle
- covered with stratified squamous epithelium
- function: perceives taste and mechanical digestion
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
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
GI Tract Layers
- 4 layers, tunics
- mucosa, submucosa, muscularis, adventita/serosa
Mucuosa
- innermost tunic
- esophagus has nonkeratinized stratified squamous epithelium
- stomach to anal canal has simple columnar epithelium
- areolar CT
Muscularis Mucosae
-thin layer of smooth muscle
Submucosa
- connective tissue
- contains major blood vessels
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
Serosa or Adventitia
- outermost layer
- serosa = visceral peritoneum + areolar CT
- adventitia = areolar CT only
Esophagus Gross Anatomy
- muscular tube that connects pharynx to stomach
- function:propel food to stomach
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
Reflux Esophagitis
- heartburn
- stomach contents back flow (reflux) into esophagus causing burning pain
- risk factors: overweight, smoking, large meals before bedtime
Stomach Gross Anatomy
- connects to esophagus and duodenum
- upper left quadrant
- main function: uses mechanical and chemical digestion to turn bolus into chyme
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
Gastric Glands
-cells that secrete gastric juice (acidic, contains HCl)
What prevents gastric juices from eating away at stomach itself?
- cells secrete layer of mucus-protective lining
- epithelium constantly regenerating
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)
Small Intestine Gross Anatomy
- functions: finishes chemical digestion process
- absorbs most (90%) of nutrients
- 3 specific segments
Duodenum
- connects to stomach
- receives chyme from stomach
- receives bile and pancreatic enzymes through duodenal papilla
Jejunum
- middle part
- connects to duodenum and ileum
Ileum
- connects to cecum of large intestine
- majority of last part of chemicals get secreted and interact with chyme
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
Villi
- folds of the MUCOSA only!
- function: increase surface area
- in center of each villus are blood vessels and a lacteal
Lacteal
- lymphatic capillary
- absorbs lipids and lipid soluble vitamins (A, D, E, K)
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
Cecum
- sac that connects to ileum
- lower right part of abdomen
- vermiform appendix attaches here
Rectum and Anal Canal
- terminal portion of large intestine
- feces leaves anal canal through anus
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
Teniae Coli
-3 thin bands of smooth muscle that bunch large intestine into sacs called haustra
Colorectal Cancer
- most arise from polyps from mucosa
- not all polyps are cancerous
- blood in stool early warning sign
- colonoscopy to examine colon
Liver
- upper right part of abdomen
- functions: produce and secrete bile, processes products of digestion
Gallbladder
- underneath liver
- function: stores and concentrates bile
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)
Pancreas
- behind stomach
- acinar cells
Acinar Cells
- secreate pancreatic juice: contains digestive enzymes, alkaline, neutralizes acidic chyme
- pancreatic juice leaves via a pancreatic duct
Billary Apparatus
-a network of “tubes” that transport bile and pancreatic juices TO the duodenum!
Arterial Blood Supply to Abdominal GI Tract
- from branches of:
1) celiac trunk
2) superior mesenteric artery
3) inferior mesenteric artery
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
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
Ducts of Billary Apparatus
- right and left hepatic ducts (from liver) unite to form the common hepatic duct
- gallbladder has a cystic duct
- cystic duct and common hepatic duct unite, forming common bile duct, it connects with pancreatic duct
- common bile duct opens into duodenum at the duodenal papilla: here, bile and pancreatic juices are secreted!
