GI System 2 Flashcards
What are some characteristics of the esophagus? (7)
Length, movement, innervation, type of epithelium
Passageway to stomach (simple squamous epithelium)
C6 (cricoid cartilage) to T7 (CC to posterior mediastinum)
Skeletal and smooth muscle (flat when empty)
Food moves via peristalsis to cardiac sphincter (stomach entrance)
Many extra glands in the submucosal layer to secrete mucus (easy passage of bolus)
Innervation: CN X, vagus nerve
What is one of the main functions of the bottom of the esophagus and how does it accomplish this (5 methods)?
Prevention of reflux and erosion
Lower esophageal sphincter
Peristaltic clearance
Stratified squamous epithelium
Submucosal glands (mucus, extra layer)
Mucus from stomach
What are the 5 regions where simple columnar epithelium is found? What are the four regions where stratified squamous epithelium is found?
- Stomach, duodenum, small intestine, large intestine, rectum
- Oral cavity, pharynx, esophagus, anus
What are some characteristics of the stomach? (6)
Location, vasculature, function (3ish), what does it make
Muscular sac that stores food temporarily
Intraperitoneal in LUQ
Vasculature/innervation from celiac trunk
Mechanically breaks down bolus via contractions of muscle wall (mix/churn- segmentation)
Chemically/ enzymatically digest food (secreted acid/ enzymes)
Mixes bolus and gastric juices into chyme (viscous, acidic, soupy)
What are the 6 anatomical features of the stomach?
Fundus: dome at top
Cardia: where the heart sits in relation to it
Body: most digestion
Lesser curvature/ omentum (inner)
Greater curvature/ omentum (outer)
Pyloric sphincter: before going into duodenum
What are the layers of muscle found in the stomach wall (3) and what is the structure found there?
3 layers of smooth muscle: middle oblique, outer longitudinal, and inner oblique (extra).
Rugae: folds made out of the simple columnar epithelium, stretch out when stomach is full (not folded) and become folded again when stomach empty
What are the five types of secretory cells found in the stomach rugae/gastric gland? What are their functions?
Surface mucus cell: closest to lumen, paint inside of stomach with thick layer of mucus to protect lining from acid
Mucus neck cell: secretions a bit more watery (serous)
Parietal cell: secrete H+ and Cl- unbonded, when they pass the secretion of mucus neck cells, they bind and are active/ acidic
Chief cells: produce pre-enzymatic proteins, not active until pass mucus neck cell secretion, then active for digestion (pepsin and lipase)
Enteroendocrine cell: through entire tube, produce gastrin and communicates with blood and activates chief cells and parietal cells to secrete
What are some characteristics of the small intestine and its three parts from closest to stomach? What are the 3 structures that help with absorption?
Location, length, to and from, function
Longest part of digestive tube (6-7m long)
From pyloric sphincter (stomach) to ileocecal valve (colon) found in all quadrants
Specialized for absorption: circular folds (plicae circulares), villi, microvilli
Mostly intraperitoneal (except most of duodenum)
Foregut and midgut structure
Duodenum, jejunum, ileum
What is the structure/location/ function/ vasculature of the duodenum? (6)
25cm, C-shaped segment, most in RUQ
Both intraperitoneal (beginning/end) and retro (middle)
Receives chyme from stomach, as well as secretions from pancreas and liver (via gallbladder)
Digestion of fat, proteins, lipids
Vasculature: anastomosis of the celiac and SMA branches
What are Brunner’s glands? (3) How is their location similar to esophagus?
Provide lots of alkaline mucus to neutralize the acid entering duodenum from stomach (in addition to pancreatic buffers)
Found in submucosal layer (similar to esophagus, only structures before and after stomach have submucosal glands to deal with high acidity)
How is the duodenum associated with surrounding organs?
What is the common opening where everything enters the duodenum? What does chyme do once it enters?
Liver: bile secreted from here, stores in gallbladder into duodenum, assists with digestion of lipids
Stomach: chyme squirted through pyloric sphincter
Pancreas: secretes enzymes that aid digestion of fats/ proteins/ carbs and bicarbonate buffer
Hepatopancreatic ampulla: sphincter needs CCK and secretin to open
Chyme: stimulates mucosa to produce hormones by enteroendocrine cells (CCK and secretin) to release the pancreatic juice and bile through above structure
What are some characteristics of the pancreas (6)? Location, vasculature, type of gland, function (2)
Posterior to stomach, between duodenum and spleen
Retroperitoneal (R/L UQ)
Vasculature: anastomosis of celiac and SMA branches
Endocrine AND exocrine gland
Secretes digestive enzymes: digest food in SI
Secretes bicarbonate buffer: neutralize acidic chyme, establish alkaline pH for pancreatic digestive enzymes to work
What are the anatomical structures of the pancreas? (7)
Main pancreatic duct into the hepatopancreatic ampulla
Head, body, tail
Abdominal aorta via splenic artery feeds it
Venous drainage: splenic vein to hepatic portal vein
What are the two functions of the pancreatic epithelial cells?
Endocrine secretion: glucagon (alpha), insulin (beta), somatostatin (delta), islets of langerhans
Exocrine secretion (pancreatic juices): pancreatic acini, water/ ions/ digestive enzymes, buffers (bicarb), neutralize chyme, breakdown ingested material
What are the two types of cells found in the pancreatic acini and what do they do?
Acinar cells: secrete digestive enzymes (amylase, lipase, proteinase), pre-enzymatic proteins
Centroacinar cells: secrete bicarbonate buffer and regulate pre-enzyme release from acinar cells
What are some characteristics of the liver? (5)
Location, size, functions, vasculature
Largest gland in the body, intraperitoneal, upper quadrants
Variety of metabolic and secretory functions
Endocrine and exocrine functions
Vasculature: celiac trunk (hepatic artery) and hepatic portal vein
What are the three major functions of the liver? (3,2,1)
- Metabolic regulation: carb, protein and fat metabolism, regulates circulating levels of everything absorbed from intestines, inactivates toxic compounds
- Hematological regulation: destroys aged/damaged RBC, cellular debris and pathogens, secretes plasma proteins into blood (osmotic concentration, nutrient support, clotting)
- Synthesis and secretion of bile: bile (water, ions, bilirubin, bile salts) required for digestion of lipids
What are some anatomical features of the liver? (7)
Right lobe (large), left lobe, gallbladder
Left hepatic vein, IVC (everything drains into here), right hepatic vein
Portal triad: 3 tubes
What is contained within the portal triad of the lesser omentum? (3) and what is the lesser omentum?
Bile duct (out): bile moving out of liver
Hepatic artery proper (in): feed liver with O2 blood
Hepatic portal vein (in): nutrient rich, no O2, gives all drainage to liver
Lesser omentum: visceral peritoneum from liver/stomach, thus thick mesentery that protects the portal triad
What is the passage of blood flow to the liver? (5)
All blood drainage from intestines flows to the liver before returning to the heart
O2 and deO2 nutrient blood mix in the liver
Delivers products of digestion directly to liver
Blood with appropriate levels of metabolites is carried from liver to IVC by L/R hepatic veins
Large lipids delivered directly to general circulation via the lymphatic system
What is the histology of the liver? (5)
Liver lobules made of hepatocytes
Portal triad at every corner
Kupffer cell (macrophage: digests RBC when damage/old
Central vein: goes to L/R hepatic vein then IVC
Sinusoid: large arterial blood vessels that mix O2 and deO2 blood with wide windows so things can come in and out
What is the endocrine function of the liver? (2)
Endocrine surface with endothelium (other set of surfaces that faces blood space)
Take up substances from blood and secrete substances into the blood
What is the exocrine function of the liver? (3)
Set of exocrine surfaces that face each hepatocyte (epithelial tight junctions)
Form small channels called canaliculi
Secrete bile into canaliculi
What is the passage of bile from the liver to the duodenum? (6) Where is bile stored?
Bile drains into canaliculi to hepatic ducts to common hepatic duct to cystic duct (gallbladder) to bile duct to duodenum
Bile from the liver is concentrated and stored in the gallbladder (muscular sac)
How is bile secretion into its various location controlled? (3)
Hepatopancreatic sphincter closed: bile flows into gallbladder via cystic duct (tense smooth muscle)
Hepatopancreatic sphincter open: bile flows into duodenum via bile duct (relaxed smooth muscle)
Main pancreatic duct picks up exocrine secretion of pancreas to the duodenum
How is the presence of chyme important in the control of bile entry into the duodenum?
Presence of chyme in duodenum induces release of hormone cholecystokinin (CCK) which induces relaxation of the sphincter and contraction of the gallbladder thus bile enters
What are some characteristics of the jejunum? Location (3), vasculature (2), beginning, function, structure
2nd segment, upper quadrants, intra, SMA and vein (midgut)
Begins at duodenojejunal flexure (tube coming back into intraperitoneal space)
Majority of nutrient absorption
Thicker walls, larger diameter, redder than ileum
Larger plicae circulares (folds) and more than ileum
What are some characteristics of the jejunum?
Final segment, lower quadrants, intra, SMA/vein midgut
Absorption of remaining nutrients
Ileocecal valve: empties into large intestine (cecum)
Lymph nodes: Peyer’s patches, protects from colonic bacteria
What are the anatomical regions of the small intestine? (3)
Circular folds: permanently folded, unlike rugae
Duodenal submucosal glands (Brunner’s glands)
Aggregated lymphoid nodule (Peyer’s patches)
What creates the large surface area of the small intestine? (3) What is the average length, diameter…
Average length: 5-6m, diameter: 2.5-4 cm
Surface area increases by 600x, over 2 mill cm sq of absorptive area
1. Plicae circulares (3x): circular folds that do not stretch like rugae, lots of jejunum
2. Villi (10x): on each fold of plicae circulares
3. Microvilli (20x): on columnar epithelium, cytoplasm of cell projected into lumen
What are the four cells on the villar epithelium and their functions from outer to inner?
Absorptive cell: main epithelial cell
Goblet cell: mucin
Enteroendocrine cell: regulators by releasing hormones, prep smooth muscle to contract, increase GC, control PC
Paneth cell: immunity, secretions kill some bacteria and determine gut flora
What molecules get absorbed into the hepatic portal circulation and how do they get in? And what do they get broken down into? (2)
Sugars –> monosaccharides
Proteins –> amino acids
Via capillaries
What molecules get absorbed into the thoracic duct? Why are they here and not in the hepatic portsl circulation? (2) What is another structure that is involved here?
Fats–> fatty acids
Chylomicrons (with bile salts) –> chyle
Too large for capillaries
Lacteal: extension of the lymphatic system to absorb fats
What are some characteristics of the large intestine?
Shape, location, function, vasculature, parts (8)
Horseshoe-shaped tube (1.5m long, 7.5cm in diameter) all quadrants
Both intraperitoneal (horizontal, transverse, cecum, sigmoid)
and retroperitoneal (ascending, descending, rectum)
SMA/IMA and veins (midgut and hindgut)
Reabsorbs water and electrolytes, and absorbs important vitamins produced by colonic bacteria (no digestive enzymes, vitK, vitB12)
Compacts and stores feces
Has its own source of enteroendocrine cells
What are the anatomical features of the large intestine from beginning and end?
Cecum (appendix), ileocecal valve, ascending colon
Right colic (hepatic) flexure (from retro to intra), transverse colon, left colic (hepatic) flexure
Descending colon, haustrum (haustra, bumps that fill with food and compacts it into its shape)
Sigmoid colon
Rectum
What is the layer of longitudinal smooth muscle layer?
Teniae coli, 3 strips around the entire tube and therefore powerful contraction
What areas of the colon are supplies by the SMA and the IMA? (5 and 4)
SMA: Cecum, ascending colon, right colic flexure, transverse colon, left colic flexure
IMA: descending colon, haustrum, rectum, sigmoid colon
What are some accessory structures present in the large intestine? (4)
Teniae coli (muscle, 3 strips)
Lymphoid nodule
Mucus glands in mucosa: goblet cells
Bacteria: breakdown fatty acids and VitK absorption
What are the 4 structures contained within the colonic epithelium?
Colonic gland (crypt)
Lymphoid nodule
Absorptive cell
Goblet cell: for lots of mucus to move waste towards the rectum
What are some characteristics of the rectum? (4)
No absorption, only temporary storage of all toxic substances (feces)
Simple columnar epithelium
15cm
Triggers the urge to defecate (into the anal canal, parasympathetic signals sphincters to relax)
What are some characteristics of the anal canal?
From non-keratinized to keratinized (skin) stratified squamous epithelium
Part autonomic (smooth muscle- internal anal sphincter)
Part somatic (external anal sphincter)
What are the muscles of the external anal sphincter and the ones that elevate the anal canal?
External anal sphincter: skeletal muscles, deep, superficial and subcutaneous
Anocutaneous line: white line, division between autonomic and somatic innervation
Internal anal sphincter: smooth muscle
Levator ani: iliococcygeus, puborectalis
