Chapter 24 Digestive
Nonkeratinized stratified squamous
mouth, pharynx, esophagus, anal canal
Simple columnar epithelium
stomach, intestines
amongst the epithelial cells
exocrine cells
collectively called enteroendocrine cells
endocrine cells (GI)
submucosal and myenteric plexus
enteric nevous system
Myenteric Plexus
plexus fo Auerbach
controls GI motility
Myenteric Plexus
lies between longitudinal and circular smooth muscle layer of the mucularis
Myenteric Plexus
Submucosal Plexus
plexus of Meissner
controls secretion of organs of GI
Submucosa plexus
lies in the submucosa adn supplies secretory cells of mucosal epithelium
Submucosa Plexus
done by the Vagus (CNX) nerves
parasympathetic
causes increase in GI secretion adn motility by increasing the activity of the enteric nervous system neurons
Parasympathetic
causes decrease in GI secretion and motility by inhibiting the activity of the enteric nervous system neurons
Sympathetic
fatty apron
Greater Omentum
Greater omentum
longest peritoneal fold; contains many lymph nodes
drapes over the transverse colon and the anterior coils of sm intestines; 4 layers
Greater Omentum
Falciform ligament
attaches the liver to the anterior abdominal wall and diaphragm
Lesser omentum
connects liver to stomach and duodenum; pathway for vessels entering liver
Mesentry
fan-shaped fold of peritoneum that binds the jejunum and ileum of sm intestines to posterior abdominal wall
most massive peritoneal fold
mesentry
extends from posterior abdominal wall and wraps around sm intestines the forms a double layer structure by returning to its origin
mesentry
Mesocolon
two separate fold of peritoneum that attach the transeverse colon and sigmoid colon of large intestines to posterior abdominal wall
hold intestines loosely in place
mesocolon and mesentry
Fauces
opening betewen the oral cavity and the oropharynx
Salivary amylase
enzyme that starts the breakdown of starch in the mouth
Saliva
contains salivary amylase, immunoglobulin A (igA), and lysozyme
lingual lipase
an enzyme that converts approx 30% of triglycerides into simpler fatty acids and diglycerides
Salivary regulation (PNS)
promotes continuous secretion of a moderate amount of saliva
Salivary regulation (SNS)
during stress, decreases saliva resulting in mouth dryness
Deglutition Center
medulla oblongata
Voluntary Stage
movement of tongue upward adn backward against the palate forces the bolus to the back of oral cavity and into oropharynx
Pharyngeal Stage
involuntary stage that begins when bolus enters the oropharynx and stimulates receptors that send impulses to the deglutition center and lower pons which cause an upward motion of soft palate and uvula to close off nasopharnyx and epligottis closes larynx
Esophageal Stage
food enters the esophagus and bolus is pushed downward by peristalsis; 1. circular muscle fibers contract pushing down bolus. 2. longitudinal fibers below bolus pushes walls out to receive bolus 3. lower esophageal sphincter relaxes and bolus moves into stomach
Rugae
large folds in the stomach that enable gastric distention
chyme
food mixed with gastric juices that creates a soupy liquid
Retropulsion
when food particles are too big to pass through plyoric sphincter and is forced back into the stomach
Surface Mucous Cells
secretes mucus
Mucous Neck Cells
secrete mucus
Parietal Cells
produces hydrochloric acid and intrinisic factor
Chief (zymogenic) cells
secrete pepsinogen and gastric lipase
G cell
secretes gastrin
stimulates parietal cells to secrete HCI
gastrin effect
gastrin effect
stimulates chief cells to secrete pepsionogen
Contracts lower esophageal sphincter
gastrin effect
increases motility of stomach
gastrin effect
Gastrin effect
relaxes plyoric sphincter
Pepsinogen
secreted by chief cells
when activated by the HCI acid, it becomes pepsin
pepsinogen
foods rich in carbs
hits the duodenum in the least amont of time
food high in protein
hits the duodenum later than food rich in carbs
food with large amounts of triglycerides
is the slowest to reach the duodenum
Acini
exocrine portion of the pancreas
cells secretes a mixture of fluid and digestive enzyme called pancreatic juice
acini
hepatopancreativ ampulla
a common dilated duct from the liver and gallbladder that enters the duodenum
Pancreatic lipase
principal lipase-digesting enzyme in adults
rapidly digests triglycerides
pancreatic lipase
splits the triglycerides into fatty acids and monoglycerides
pancreatic lipase
Liver
divided into 2 lobes by the falciform ligament
falciform ligament
suspends the liver from diaphragm and anterior abdominal wall
Lesser omentum
anchors liver to the stomach
Hepatocytes
liver cells that produce bile
Bile caniculi
small ducts that collect bile produced by heptacytes and transfers the bile into bile ducts
Common hepatic duct
where the right and left hepatic ducts unite and exit the liver
delivers the bile into the duodenum of sm intestines to assist in digestion
common bile duct
Common bile duct
formed by the hepatic duct that joins the cystic duct from the gallbladder
Hepatic acinus Zone 1
hepatocytes are the closest to the portal triad branches and first to receive nutritents, O2 and toxins
first cells to store glucose as glycogen and to show morphological changes following bile duct obstruction or toxin exposure
Hepatic acinus Zone 1
last ones to die and first to regenerate
Hepatic acinus Zone 1
Hepatic Acinus
smallest structural and functional unit of the liver
Hepatic Acinus Zone 3
farthest from the branches of the portal triad
first cells to show effects of impaired circulation and last to regenerate
Hepatic Acinus Zone 3
first to show evidence of fat accumulation
Hepatic acinus Zone 3
Hepatic Acinus Zone 2
have characteristics intermediate between the cells in Zone 1 and Zone 3
provides oxygenated blood
Hepatic Artery
provides deoxygenated blood w/ absorbed nutrients, drugs, microbes, and possibly toxins from the GI tract
hepatic portal vein
Bilirubin
principal bile pigment
derived from heme of broken-down RBC
bilirubin
secreted into bile and broken down in intestines
Bilirubin
when broken down, one product is stercoblin
bilirubin
Bile
important in emulsification of fats; stored in gallbladder until needed
alkaline, yellow-brownish liquid consisting of mostly water, bile salts, cholesterol, lecithin (phospholipid), bile pigment and several ions
bile
pear shaped sac that lies in a depression on the posterior surface of liver
gallbladder
Gallbladder
assist in digestion in sm intestine by the bile delivered by the common bile duct
Peyer's Patch
groups of lymphatic nodules that are seen in the ileum
folds of the mucosa and submucosa; begin at proximal portion of duodenum and extend to the mid portion of ileum
Circular Folds (plicae circulares)
circular folds (plicae circulares)
enhance the absoprtion by increasing the surface area and causing chyme to spiral as it passes thru sm intestines
villi
finger-like projections of the mucosa that increase the surface area of the epithelium for absorption
covered with epithelium and a core of lamina propria which contatins an arteriole, a venule, blood capillary network, and lacteals
villi
nutrients absorbed by the epithelial cells that will pass thru blood capillaries or lacteal to enter blood or lymph
Villi
Microvilli
small projections from apical membrane of absorptive cells of villi
forms a brush border that extends into the lumen of sm intestines
microvilli
greatly increases surface area of membrane so larger amounts of nutrients can be absorbed
microvilli
has several brush border enzymes for digestive functions
microvilli
Enteropeptidase
brush border enzyme which splits off part of the trypsinogen to create trypsinogen
Brunner's gland (duodenal glands)
located in the submucosa that secretes alkaline mucus that help neutralize the acidic chyme from stomach
Paneth Cells
epethelial cells in sm intestine that secretes lysozyme; capable of phagocytosis; helps regulate microbial population
Crypts of Lieberkuhn (intestinal glands)
cells that line the crevices that secretes intestinal juice
Chylomicrons
long-chain fatty acids and monoglycerides combined to form triglycerides which become coated with proteins
enters lacteal and are transported to thoracic duct and then into left internal jugular adn subclavian
chylomicrons
Micelles
formed from bile salts
tiny spheres that surround fatty chains acids and monoglycerides for absoprtion; Vit DAKE
Micelles
Teniae Coli
located in colon; thickened forming bonds portions of the longitudinal smooth muscle in the muscularis
Haustra
patches that are created by contractions of the teniae coli
Omental appendices
located in serosa in colon; visceral peritoneum filled with fat
gastroileal reflex
reflex that happens right after meals that intensifies peristalsis in the ileum and forces any chyme into the cecum
stimualted by the presence of food in the stomach and gastric peristalsis
gastroileal reflex
Colon
greatest contribution is absorption of some water, ions, and vitamins
Vitamin K and some Vitamin Bs
produced in colon
cephalic phase (digestion)
prepares stomach and mouth for food to be eaten and stimulates gastric secretion and motility
Gastric phase (digestion)
neural and hormonal mechanisms promote gastric secretion and gastric motility
Intestinal phase (digestion)
neural and hormonal mechanisms control movement of chyme has inhibitory effects that slows the exit of chyme from the stomach
CCK (cholecystokenin)
secreted by CKK cells in sm intestines in response to amino acids in partially digested triglycerides found in chyme
stimulates secretion of pancreatic juice rich in digestive enzymes
CCK
Secretin
increase secretion when acidic chyme enters the sm intestines
stimulates secretion of pancreatic juice rich in bicarbonate ions to buffer acidic stomach chyme
secretin
Gastrin
released from the G cells of gastric glands
secretes in repsonse to; distension of stomach, partially digested protein in chyme, high pH of chyme; acetycholine released by PNS neurons
gastrin
stimulates secretion of gastric juice which is inhibited when pH drops below 2.0 and stimulated when pH rises
gastrin
segmentation
localized mixing contractions seen where the intestine has been distended by lrg amount of chyme
chyme is mixed w/ digestive enxymes and brings food particles in contact w/ the mucosa for absorption
segmentation
occurs more rapidly in the duodenum
segmentation
mucosa
inner lining mucus membrane of the GI tract
composed of epithelium, connective tissue (lamina propria), muscularis mucosa (smooth muscle)
mucosa
lamina propria
contains most of the mucosa-associated lymphatic tissue (MALT)
muscularis Mucosa
small folds in mucus membrane of stomach adn intestines to increase surface area for digestion and absorption
Submucosa
binds mucosa to the muscularis
contains many blood vessels and lymphatic vessels that receive absorbed fat
submucosa
muscularis
in the mouth, pharynx, superior and middle part of esophagus contains skeleton muscle for voluntary swallowing
an inner sheet of circular fibers and outer sheet of longitudinal fibers
smooth muscle of GI tract
Adventia
single layer of connective tissue in the esophagus
Serosa (visceral peritoneum)
a serous membrane composed of areolar connect tissue and simple squamous epithelium (mesothelium)
superficial layer found in portions of the GI tract that are suspended in the abdominal cavity
serosa (visceral peritoneum)