Chapter 17 Flashcards
Define digestion?
Digestion refers to the mechanical and chemical breakdown of foods.
Define Ingestion?
Taking food into the mouth.
What are the 3 phases of eating?
- Cephalic
- Gastric
- Intestinal
Define absorption?
The passage of digested food from the GI tract into the bloodstream for distribution to cells.
What are the organs of alimentary canal?
Mouth
Pharynx
Esophagus
Stomach
Small and Large Intestines
What is meant by the “Movement of Food”?
the passage of food along the Gastrointestinal (GI) tract.
What is defaction?
the elimination of undigested material from the GI tract
What is rugae?
Mucosal folds in the stomach
What are the regoins of the stomach?
- Cardiac region – around esophagus
- Fundic region – upper area.
- Body region – main, central region
- Pyloric region – near duodenum
What are the acessory organs of alimentary canal?
Salivary Glands
Liver
Gall Bladder
Pancreas
How does food move through the esophagus?
Food moves through by:
- Gravity
- Peristaltic waves down the esophagus to the gastro-esophageal sphincter.
- Sphincter muscle relaxes
- Food moves into stomach.
What is emulsification?
- The process of breaking apart fat lobules into small droplets.
- This increases surface area and increases the effectiveness of lipases.
What is bile composed of?
- Bile salts
- Bile pigments
- Cholesterol
- Electrolytes
What is the uvula?
Extension of the soft palate
What are the four layers of alimentary canal starting with innermost.
- Mucosa
- Submucosa
- Muscularis
- Serosa
Describe the Mucosa layer of the alimentary canal.
innermost layer.
Composed of epithelium and areolar.
Epithelium extends into lumen = microvilli.
Contains glands that secrete mucous.
Functions: protection, secretion, and absorption.
Describe the submucosa layer of the alimentary canal.
beneath the mucosa.
Composed of areolar, blood and lymph vessels, and nerves.
Functions: nourishment of the mucosa and transportation of nutrients.
Describe the muscularis layer of the alimentary canal
2 layers of smooth muscle.
Circular muscle layer around the submucosa.
Longitudinal layer around the circular layer.
Function: movement of food through canal.
Describe the serosa layer of the alimentary canal.
Serosa – outermost layer.
Visceral peritoneum
Functions: lubrication and movement of canal in abdominal cavity.
Mesentery – intestinal peritoneal extensions that extend the length of the intestine.
Describe segmentation (mixing)
Food and digestive juices and mucous
Circular muscle layer.
Mixing movements due to occasional, random contractions in small “segments” of the canal.
Describe Peristalsis
Longitudinal muscle layer
Propelling action
As food passes, one section of the tube relaxes, opening next section and food moves on.
What is the gastroesophageal sphincter located?
Located between the esophagus and stomach
Where is the pyloric sphincter located?
Located between the stomach and small intestine
Where is the lleocecal valve (sphincter) located?
Located between the small and large intestine
Where are the internal/external anal sphincter located?
Located between the large intestine and
the exterior
What are deciduosus teeth? How many are there and when do they form and/or fall out?
baby teeth.
Approximately 20
Form between 6-32 months
Lost between ages 6-12.
What are Permanent (secondary) teeth? How many are there and when do they form and/or fall out?
Approximately 32
Form from age 6-adulthood
Permanent
What are the function of the teeth?
Functions: break food into smaller pieces.
Increases surface area of food.
Increase effectiveness of digestive enzymes
What are the four kinds of teeth and their function?
Incisors – front teeth; break food into bite-size pieces.
Cuspids = canine teeth; grasp and tear food.
Bicuspids and Molars = grinding of food particles.
What are the four componements of teeth?
Crown – exposed area of the tooth.
Root – area below the gum.
Enamel – covering on crown; calcium salts.
Dentin – bulk of the tooth.
What is the funciton of salivary glands?
To secrete saliva which moistens and dissolves food particles, binds them together, and beginss carbohydrate digestion via the enzyme amylase.
Triggered by the PSN at the smell/sight of food.
What do the parotid glands (salivary gland 1) produce?
A watery fluid rich in amylase
What does submandibular gland (salivary gland 2) produce?
A viscous, clear fluid.
What does sublingual gland (salivary gland 3) produce?
A mucous-like fluid.
What does salivary amylase do.
Break down carbohydrate into sugars
What are the two cells that compose salivary glands?
Mucous and serous cells
What is the Pharynx?
A connection between the nasal and oral cavities with the larynx and esophagus.
In both digestive and respiratory systems
Involved with swallowing (deglutition)
What is a bolus?
Food that mixes with saliva at the back of the pharynx.
What are the three events of swallowing (deglutition)?
Epiglottis closes over larynx.
Muscles in lower pharynx relax.
Esophagus opens and food moves in.
function of the pancreas.
Secretes pancreatic juice into ducts that lead into the duodenum.
What happens durring liver metabolism?
- Formation of lipoproteins.
- Synthesis of cholesterol and phospholipids.
- High rate of oxidation of fatty acids to supply energy for other bodily functions.
- Gluconeogenesis
Provide the function of the gallbladder
Site of bile storage
Bile is realeased into the duodenum from either the liver or the gallbladder
What are the parts of the colon?
The colon is divided into 4 portions:
- Ascending colon – from cecum to liver.
- Transverse colon – runs across the top of the abdomen.
- Descending colon – from spleen downward.
- Sigmoid colon – S-shaped portion which becomes the rectum.
Discuss the nerves control of Digestion
Montiors the stomach, allows for self control.
Lies within the wall of the gut
One plexus lies b/w the longitudinal & circular muscle layers
Controls the movement of the GI tract
Another plexus lies within the submucosa-controls he GI secretion & local blood flow
What are the parts of the large intestine?
- Cecum – follows the ileum; gives rise to the appendix.
- Colon – the main portion of the L.I.
- Rectum – distal region of the colon
- Anal Canal – narrowing of rectum and opening to the outside for defecation.
What are some characteristics of microvilli?
- contain the majority of enzymes needed to break down the disaccharides and polysaccharides.
- contain peptidases responsible for the break down to individual amino acids.
- absorbs the glycerol and FAs
What are the components of gastric juice?
- Mucous
- Digestive enzyme:
- Pepsin – protein digestion
- Hydrochloric acid (HCl)
- Denatures proteins
- Kills microbes in food
- Intrinsic Factor – Aids in the absorption of Vitamin B12
- Gastrin – regulatory hormone that stimulates gastric secretions
What are the 4 types of cells in the stomach?
- Mucous – secrete mucous.
- Chief cells – secrete pepsinogen
- Parietal cells – secrete HCl and intrinsic factor.
- G-cells – secrete gastrin.
What is the Enterogastric Reflex?
signals from the small intestine to stomach to inhibit stomach motility and secretion.
What does CCK do?
Cholecystokinin- produced by the duodenum during the cephalic and gastirc phases
Stimulates pancreatic digestive enzyme release
What happens when CCk is released?
Causes the release of bocarbonate ions into the duodenum
What does the S.I secrete?
Secretes:
Mucous
Peptidases
Sucrase, Maltase, Lactase(Disaccharides -> Monosaccharides)
Lipases(TG ->2 fatty acids & monoglyceride)
Discuss the regulation of the S.I
Secretions are mainly controlled by local nervous reflexes
Hormones CCK & secretin promote the secretion of S.I
Discuss the movement of S.I
Both movements of the alimentary canal are seen at the S.I
Segmentation for mixng the chymes and intesinal juice
Peristalsis push residual chyme toward the ileoceal sphincter, through the alimentary canal
discuss thefunction of the L.I
- Absorption of water and electrolytes
- Secretion of mucous which conatins large amounts of bicarbonate ions
- Storage of feces
Discuss the regulation and movement of L.I
Regulation: secretions and movements are mainly controlled by tactile stimuation controlled by local reflexes
Perislatic waves of L.I move residual chyme toward anal sphincter muscles
Give the the structure of the liver
Contains 2 lobes
Large Right & Small Left
Each lobe is made of hepatic lobules
What is the functional unit of the liver?
heptaic lobule
Discuss the blood supply of the liver
Hepative artery: supplies oxygenated blood
Heptaic portal vein: supplies deoxygentated blood filled with:
absorbed nutrients from the S.I
Toxins from the stomach
Damaged RBC
Blood enters the liver sinusiods where hepatocytes removed the following:
Oxygen, Nutrients, Toxins, Damaged RBC
Blood leaving liver cells drains into central veins which come together & leave the liver via the hepatic portal vein
Discuss the functions of the Liver
The liver has a vast array of functions:
Metabolism
Storage of glycogen, fat soluable vitamins
filters blood
detoxification
production and secretion of bile
4 classes of enzyme and define from pancreatice juice
Pancreatic Amlayse
Pancreatic Lipases
Trypsin & Chymotrypsin
Nucleases
Secreation of bicarbonate ions and water
What is the function of the mouth?
Represents the first part of the alimentary canal. Serves to receive food and beings mechanical disgestion of the food via mastication (chewing).
What is the enteric nervous system and what is its function?
The enteric nervous system monitors the stomach and allows for self control. It also lies within the wall of the gut.
What is the palate?
- roof of the mouth
- hard palate - anterior portion
- soft palate - posterior portion
What are palatine tonsils?
Masses of lymphatic tissue lateral to the palatine
What are pharyngeal tonsils?
Lymphatic tissue on the posterior pharynx
List the chemicals that stimulate gastric secretion & how
ACh: released by the vagal nerve; binds to parietal cells & mucous cells to stimulate secretion
Gastrin:binds to parietal cells increasing the secretion of HCl
Histamine: binds to parietal cells. Histamine is required for proper activity of gastrin and ACh
The mouth is composed of what 2 layers?
- Oral Cavity - chamber that extends from teeth/gums to pharynx 2. Vestibule - narrow space between the teeth, check and lips.
List the chemicals that inhibit gastric secretion and how
Sharp decreases in pH at the duodenum
Inhibitory reflexes such as the enterogastric reflex
somatosatin- inhibits gastric production
Histamine blocker
What are the parts of the small intestine?
There are 3 sections of the small intestine: * Duodenum – nearest to the stomach * Jejunum – middle region * Ileum – near the large intestine Distal end of the ileum narrows to form the ileocecal valve.
Carbohydrates digestion
Mouth: Salvary amlyase breaks down starch into smaller sugars
Stomach:No digestion of CHO
S.I: pancreatic amalyse digests most CHO into small sugasrs
Microvilli: contain the majority of enzymes needed to break down the disacchrides and polysacchrides
Liver: monosacchrides absorbed into the portal blood where it gets converted to energy or stored as glycogen
Protein digestion
Mouth: no digestion
Stomach:pepsin begins the process of breaking down proteins
S.I: trypsin & chymotrypsin released from the pancreas, break down proteins into peptide chains
Pepitdases: break down peptide chains into 2-3 amino acid chains
Microvili: contain peptides responsible for the break down to individual amino acids
Liver: amino acids are absorbed through the portal blood
Fat digestion
Mouth – No digestion
Stomach – Little to no digestion of fats (lipase).
S.I. – major site of fat digestion. Emulsification of lipids by bile salts, forming a micelle.
S.I.:
Pancreatic Lipase – breaks down TGs into glycerol and three fatty acids.
Bile removes the glycerol and FAs when they are formed, forming micelles.
Micelles move to the microvilli
Microvilli – absorbs the glycerol and FAs.
TGs are reformed in the ER to form a chylomicron.
Chylomicrons are moved to the central lacteal of the villi where it is then put into the lymph then to the blood.
Liver: Receives the chylomicrons and reconstructs TGs and stores.
Lipids are used as an energy source, formation of ketone bodies and synthesis of cholesterol.
4 Types of Lipoproteins: VLDL, DL, LDL, or HDL - cholesterols
Nucleic Acid Digestion
Mouth – no digestion
Stomach – no digestion
S.I. – break down, via pancreatic nucleases, into nucleotides.
Liver – absorbed through the portal blood system.
What casues secretin to be released, and what does it do?
Secretin is released:
In response to a decrease in pH at the duodenum & jejunum
This stimulates the realease of bocarbonate fluid and some pancreatic enzymes into the duodenum
