Lecture 21 4/17/14 Flashcards
Mastication
Chewing Food
Deglutition
Swallowing Food
Espophagus
1 ft long
Runs from Pharynx to stomach
Posterior to trachea. Passes through opening in diaphragm called esophagus hiatus
Stratified squamous epithelium
What is the Muscular Composition of Trachea
Upper 1/3 - Skeletal Muscle (Voluntary contraction of swallowing)
Middle 1/3 - Mixed Muscle
Lower 1/3 - Smooth Muscle (Peristalsis wave to involuntary contraction)
What is the Mechanism of Swallowing
Peristalsis
Define Peristalsis
a muscular wave of digestive tube that pushes food forward.
What is the stomach’s job?
job is store all the food we’ve eaten, as we digest it
Function of the Stomach?
Stores food
Breaks down food mechanically (physical chewing)
Breaks down food chemically (digestive enzymes)
Define Chyme
mixture of gastric juices or acids and food material, digestive enzymes, food material.
Describe the Anatomy of the Stomach
Innermost oblique layer. Inner oblique. Myenteric Plexus or called the Auerbach Plexus.
Rugae
folds that line the stomach. Muscular fold that line the lumen of the stomach when empty.
Serves as an accordion pleats will allow for enlargement of the stomach to accommodate the increase in food.
It’s present when the stomach is empty, and disappear when the stomach gets full.
Stomach wall is composed of what?
the same four basic layers as the rest of the digestive tract. Only difference is the muscular tunic which has 3 layers.
What is the three layers of the Muscular Tunic
Outer Layer - longitudinal
Middle Layer - Circular
Inner Layer - Oblique
Gastrin ramps up what?
Digestion
Pepsinogen is what type of precursor?
Enzyme
Protein digestion starts where?
In the stomach
Inactive Pepsinogen
coverts to pepsin in the presence of HCl
What activates pepsinogen?
HCl pH level of 1.5 - 2.0
Intrinsic Factor
Helps absorb Vitamin B12
Gastric Lipase
Fat Breakdown
Chief and Parietal Cells secrete how much gastric juice per day?
150 ml
Enteroendocrine Cells
Reside within the gastric pit, secrete 6 different known substances
Gastrin
Main regulatory hormone
A polypeptide hormone released when food enters stomach.
Starting hormone, ramps up hormone for digestion
3 Phases of Regulation of Gastric Function
Cephalic Phase
Gastric Phase
Intestinal Phase
Cephalic Phase
sight, smell, taste causes CNS to stimulate vagus nerve. This PNS stimulation increases gastric motility and secretion of juices. Your brain realizes that you’re about to eat, and it activates an area of the brain called vagi. Cranial Nerve 10, involved in resting and digestion. 20% of secretion occurs here.
Gastric Phase
arrival of food to stomach. Increases muscular contraction, gastric secretion causes increased motility. 80% of secretion is the end Result. Acid, pepsinogen and gastric lipase increase when food materials comes into contact with the stomach.
Intestinal Phase
Begins as chyme enters the duodenum. Purpose: control rate of gastric emptying mostly inhibitory process. Then dumps into the small intestine.
Cholecystokinin’s main job
Job is to maintain digestion and causes the gall bladder to contract or secrete bile.
Enterogastric Reflexes
if the duodenum is full then these reflexes suppress motility and gastric activity.
Arrival of Chyme causes what?
enteroendocrine cells of the small intestine to inhibit gastric secretions.
Cholecystokinin causes what?
Is a Peptide hormone causing:
1) pancreas to release digestive juices
2) gall bladder release bile
3) inhibit gastric activity
Secretin
tells pancreas to secrete an alkaline buffer. Slows down the process.
Gastric Inhibitory Peptide
Glucose dependent insulinotropic peptide which initiate release of insulin from pancreas.
Pancreas
Soft, approximately six inches long
Location is posterior and inferior to stomach
Glandular Tissue
Acinar Cells that produce the digestive enzymes
Acinar Cells
Make up the majority of the pancreatic tissue.
Form the exocrine portion of the pancreas.
Digestive Enzymes
Alpha Amylase
Pancreatic Lipase
Nucleases
Proteases
Alpha Amylase
Digest Carbohydrates
Pancreatic Lipase
Lipases
Nucleases
DNAse and RNAse
Proteases
Trypsin, Chymotrypsin, Carboxypeptidase (absorbed in bloodstream)
Digest proteins in the stomach that go into the small intestine
Secretin
Why chyme enters the duodenum, secretin is released which causes alkaline solution to release and to neutralize stomach acid entering the small intestine
Pancreatic Juice
Alkaline with a pH of 7.5-8.8
Islet of Langerhans
clusters of cells residing within the acinar cells. They are ductless - endocrine.
Alpha Cells
Glucagon increase blood sugar
Beta Cells
Insulin decreases blood sugar
Liver
Largest visceral organ within the human body
Approx. 4 lbs
L&R main lobes with Right lobe bigger
Separated by Falciform ligament
Predominantly within the upper right quadrant of the abdomen under diaphragm
Hepatic Portal Vein
Nutrient Rich unoxygenated blood
Hepatic Artery
Oxygenated blood
Common Bile Duct
formed by the union of the common hepatic duct and the cystic duct (from the gall bladder)
Lobules of the Liver
the liver is divided into microscopic units called lobules. They consist of cords of liver cells called hepatocytes, which are arranged in a radial pattern around a central vein.
Sinusoids
spaces between the cords through which blood passes.
Kupffer Cells
Stellate reticuloendothelial cells. Phagocytes - Part of the immune system. Type of Resident macrophages. Job is to clean the blood
Blood Flow of the Liver
Blood goes from the intestines, hepatic portal vein to the liver, hepatic veins from the liver to inferior vena cava then back to the heart.
Hepatic Artery
O2, Nutrient rich relatively from Celiac Trunk
Hepatic Portal Vein
O2 deficient, nutrient rich from digestion
Blood Flow from the Hepatic Portal Vein
Goes from the Hepatic Portal Vein -> Sinusoids -> Central Vein -> Hepatic Vein -> Vena Cava.
Bile Flow
Left and Right hepatic ducts come together to form the -> common hepatic duct -> Gall Bladder and the Gall Bladder duct is known as the (Cystic Duct) -> common bile duct -> joins with main hepatic duct
Metabolic Regulation of Liver Function
monitors circulatory levels of metabolites and adjusts them. Toxins and other metabolic wastes are also removed. Fat soluble and vitamins are stored
Hematological Regulation of Liver Function
The liver is the largest blood reservoir in the body. Stores blood, removes aged and damaged Red Blood Cells
Synthesis and Secretion of Bile of Liver Function
hepatocytes. Bile is composed of bilirubin, cholesterol, ions lipids, and water. It is created from the recycling of the heme from RBC’s and it is required for the normal digestion of fats.
Enterohepatic Circulation
90% of all bile is reabsorbed and returned to the liver via the hepatic portal system
Secretion of Bile
stimulated by cholecystokinin in response to fat in the intestines.
The Gall Bladder
a small sac located on the underside of the liver. Cholecystokinin causes contraction of gall bladder and relaxation of sphincter.
Function of Gall Bladder
Store and concentrate bile
Small Intestine
Approximately 20 ft long, begins at pyloric valve and ends at the cecum, majority of the absorption occurs here.
3 Division of Small Intestine
Duodenum
Jejunum
Ileum
Duodenum
approximately 1 ft long, first part of the small intestine. Receives chyme from stomach and exocrine secretions from pancreas and liver.
Brunner’s Glands of Duodenum
submucosal glands that aid in the production of mucus with buffers to elevate pH of acidic chyme. pH goes from 1-2 to 7-8.
Secrete a bicarbonate solution to help neutralize the acidic chyme coming into the duodenum. That’s the function of the brunner’s glands, producing this material.
Duodenal Papilla of Duodenum
Pancreatic and bile juices mixed with chyme in duodenum
Jejunum
next region of small intestine, approximately 8 ft long, most of the absorption occurs here.
Ileum
Last region of the small intestine, approximately 12 ft long
Peyer’s Patches of Ileum
20-30 of them. A collection of lymph nodules that prevent proliferation of bacteria in small intestine.
Lymphoid tissue. Located distal portion from the ileum. Involved in Mediating our immune system function with the bacteria that is in the digestive tract.
Symbiotic relationship. Different bacteria in the small intestine and different bacteria in the large intestine. Wanna keep the bacteria separated from each other.
Four Layers of Small Intestine
Plicae
Villi
Microvilli
Crypts of Lieberkuhn
Plicae
transverse folds; increase the surface area
Villi
finger like projections; increase the surface area
Microvilli
each villum is covered by simple columnar epithelium. Each cell has microvilli on its’ surface. Serves to increase surface area.
Crypts of Lieberkuhn
AKA Intestinal Glands; Cells are going to be highly mitotic. Dividing to move upward to replenish whats destroyed on the surface of the villi.
Pits in the intestinal wall perform 3 functions
- Reproduce and replace the columnar and goblet cell epithelium that is shed from abrasion during the digestive process called exfoliation.
- Produce Enterokinase - hormones that activate pancreatic enzymes
- Contain Enteroendocrine Cells - produces various hormones including cholecystokinin and secretin. G-Cells, I-Cells, etc.
Lacteal of the Villi
Terminal lymphatics that transport materials that do not enter capillaries because of their large size. ie Fatty acids
Chylomicrons of Villi
protein lipid packages that transport fatty acids through the lymphatic system and blood system.
Mechanical Digestion of Villi
movements of the muscular tunic. Small intestine is lined by smooth muscle.
Rhythmical Segmentation
contraction of the circular fibers in various locations on and off to divide small intestine into fragments. Occurs 12-16 times per minute to move or slosh chyme back and forth.
Pendular Movements
contraction and relaxation of the longitudinal fibers causing the movement of Chyme.
Propulsive Peristalsis
a peristaltic wave the propels chyme forward through the intestines.
Chemical Digestion
- Carbohydrates
a. Mouth - salivary amylase begins sugar breakdown
b. Duodenum - pancreatic amylase continues sugar breakdown then absorbed in small intestines. - Proteins
a. Stomach - pepsin breakdown of proteins into short chain amino acids
b. Small intestine - chymotrypsin, trypsin, carboxypeptidase continue protein breakdown.
Vitamins
a. Water soluble vitamins are easily absorbed through the intestinal epithelium.
b. Fat soluble vitamins are absorbed with lipids. A, D, E vitamins.
Large Intestine
approximately 5 ft long
Cecum
First portion of the large intestine. Separated from the ileum by the ileocecal valve, which regulates digestive flow from small intestine into the large intestine.
Vermiform Appendix
extends from the bottom of the cecum, approximately 3-4 inches long, a blind end, hollow tube made of lymphatic tissue. Appendicitis. Vermiform means worm.
Large Intestine Anatomy
Cecum Ascending Colon Transverse Colon Descending Colon Sigmoid Colon Rectum Anus
Microscopic Anatomy of the Large Intestine
Contain fewer plicae and villi, but is lined with columnar epithelium, and many goblet cells to secrete mucus movement of fecal material.
Functions of the Large Intestine
Movement of Colon Contents
Peristalsis
Absorption and Fecal Formation
Defecation
Movement of Colon Contents
Haustral Churning - the haustra distend and relax as they squeeze their contents to the next haustral segment.
Peristalsis
Peristaltic movement occur here as they occur in the small intestine, but mass peristalsis is also observed. This is a strong wave that drives fecal contents into the rectum.
Absorption and Fecal Formation
Bacteria aid in the final decomposition of remaining proteins and breakdown bilirubin into a brown pigment. Bacteria also aid in the synthesis of various vitamins. The large intestine is vital in maintaining the body’s water balance. The majority of water absorption occurs here. This also converts the fecal material into a semisolid waste ready for elimination.
Defecation
Mass Peristaltic waves push fecal material into the rectum. This stimulates pressure sensitive receptors to initiate the defecation reflex. Fecal pressure in the rectum causes relaxation of the internal anal sphincter (smooth muscle), and contraction of the external anal sphincter (skeletal muscle). Conscious release of the external anal sphincter allow defecation to occur.
