Digestive system Flashcards
The digestive tract begins and ends where?
begins - oral cavity - mouth
ends - anus
what are the six functions of the digestive system?
- Ingestion – takes place when food enters the mouth (oral cavity).
- Mechanical processing (or mechanical digestion) – involves crushing and shearing food and then propelling the food along the digestive tract.
- Digestion (or chemical digestion) – chemical breakdown of food into small molecules that are suitable for absorption.
- Secretion – release of water, acids, enzymes, buffers, and salts by the epithelium of the digestive tract, glandular organs, and the gallbladder.
- Absorption – movement of substances across the digestive epithelium that lines the small intestine. Substances move from the lumen to the interstitial fluid.
- Excretion (or defecation) – removal of waste products from body.
What are the Major organs of the digestive system?
oral cavity small intestine large intestine stomach pharynx esophagus
What are the accessory organs of the digestive system?
teeth salivary glands gallbladder pancreas tongue liver
The digestive tract contains four layers of tissue. What is the name of each layer of tissue and where is each layer located relative to the lumen?
- mucosa - closest to the lumen
- submucosa - 2nd closest to lumen
- muscularis externa (or muscular layer) - 3rd closest to lumen
- serosa - furthest from lumen
Which layer of the digestive tract wall contains epithelial cells?
Mucosa
What type of epithelial cells are found in the stomach and intestines and what is the function of these epithelial cells?
simple columnar epithelial cells; absorption and/or secretion
What types of specialised epithelial cells are found in the epithelial lining of the stomach and intestines?
stem cells
enteroendocrine cells
goblet cells
Paneth’s cells
What is the function of the muscularis externa (or muscular layer) of the digestive tract?
involved in the mechanical processing of food and movement of materials along the digestive tract
Name the two types of motility (movement) in the digestive tract.
segmentation
peristalsis
Describe peristalsis
peristalsis - a propulsion process involving waves of smooth muscle contraction that move compacted ingested materials (e.g. bolus) along the digestive tract.
Describe segmentation
cycles of smooth muscle contraction and relaxation that churns and fragments the bolus to mix the contents of the bolus with secretions (e.g. enzymes).
The oral cavity (mouth) is the first part of the digestive tract that is exposed to food. What are the functions of the oral cavity (mouth)?
ingestion of food
sensory analysis of ingested material
mechanical processing of ingested material
limited chemical digestion
lubrication
what are the functions of saliva?
lubrication of the mouth and pharynx
- cleanse the mouth and teeth
- moistening of food
- limited chemical digestion (i.e. break down starch (carbohydrate) and lipids)
Which glands produce saliva?
Sublingual glands
Submandibular glands
parotid glands
After leaving the oral cavity (mouth), which structures does food pass through on the way to the stomach?
Food passes from the oral cavity (mouth) to the pharynx, esophagus, and then the stomach.
The stomach performs mechanical processing (or mechanical digestion) of materials that enter the digestive tract. Which of the following terms describes the partially-digested food/fluid in the stomach?
Chyme
Function of the Stomach
Carbohydrates digestion
Protein Digestion
Storage and mixing chamber
triglyceride digestion
What type of muscular tissue is found in the walls of the stomach?
Smooth muscle only
The mucosa of the stomach contains four types of secretory cells. What is the name of each type of secretory cell and what substance does each type secrete?
Mucous cells - mucus
Parietal cells - hydrogen chloride (HCl)
Chief cells - pepsinogen
G cells - gastrin
The regulation of gastric activity involves three overlapping phases. What are these phases called?
cephalic, gastric, and intestinal phases
The sight, smell, taste, or thought of food is the beginning of which phase of regulation of gastric activity?
cephalic
Cephalic phase, the sight, smell, taste, or thought of food leads to increased secretion of which substances into the stomach?
gastrin, mucous, hydrogen chloride (HCl), and pepsinogen
What is the function of the cephalic phase of regulation of gastric activity?
prepares stomach for arrival of food
What marks the beginning of the gastric phase of regulation of gastric activity and what is the function/purpose of this phase?
beginning: arrival of food into the stomach
function/purpose: increases gastric motility
The gastric phase of regulation of gastric activity involves increased secretion of which substance/s?
gastrin
mucous
hydrogen chloride (HCl)
pepsinogen
What is the beginning of the intestinal phase of regulation of gastric activity?
chyme entering the duodenum
In the intestinal phase of regulation of gastric activity, chyme entering the duodenum stimulates increased secretion of
secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP)
What is the function of the intestinal phase of regulation of gastric activity?
control rate of gastric emptying (from stomach to duodenum)
What are the three regions of the small intestine?
ileum
duodenum
jejunum
What does the Ileum do?
nurtrients absorption only
no chemical digestion
Function of the Duodenum
receives chyme from the stomach which mixes with digestive enzymes and buffers from the pancreas
Function of the Jejunum
chemical digestion occurs here and the majority of nutrient absorption
List 3 features of the small intestine that increase the surface area, and therefore increase the amount of absorption that can occur.
Length (approx 6 m)
Circular folds (also known as plicae circulares)
Villi (finger-like projections of mucosa)
Microvilli (extensions of the plasma membrane of absorptive cells; form a brush border)
What type of epithelial cells cover the villi in the small intestine?
Simple columnar
Name the four layers of tissue that make up the wall of the small intestine and state where each layer is located relative to the lumen?
- mucosa - closest to the lumen
- submucosa - 2nd closest to lumen
- muscularis externa (or muscular layer) - 3rd closest to lumen
- serosa - furthest from lumen
Movement of food/material along the small intestine (i.e. motility) occurs via peristalsis and segmentation. Both peristalsis and segmentation involve contraction of smooth muscle located in the walls of the small intestine. What are the characteristics of these two types of motility?
Peristalsis - Propels bolus forward Segmentation - mix bolus with intestinal secretions - mixing/churning of bolus - breakup/fragment of bolus - non-directional movement of bolus
What are the two parts of the pancreas called?
endocrine pancreas and exocrine pancrea
Which part of the pancreas is involved in digestion?
Exocrine pancreas
How do pancreatic secretions drain into the digestive tract and where does this occur?
Pancreatic secretions (i.e. pancreatic juice and digestive enzymes and buffers) drain into the duodenum via the pancreatic duct.
Exocrine characteristics/functions
secrete digestive enzymes and buffers into duodenum controlled by secretin duodenal hormone function: aid digestion controlled by CCK duodenal hormone secrete pancreatic juice into duodenal contains acing glands
endocrine characteristics/functions
function: blood glucose homeostasis
secrete glucagon and insulin into blood
contain pancreatic islets
what is the name of the two functions of the liver
metabolic and haematological
metabolic functions
process drugs protein metabolism lipid metabolism carbohydrates metabolism store minerals and vitamins
Haematological functions
make plasma proteins
remove hormones
remove old blood cells
remove toxins from blood
What type of cells are found in the liver?
hepatocytes and Kupffer cells
What substance is produced in, and secreted by, the liver and stored in the gall bladder?
bile
What is the function the substance that is produced in, and secreted by, the liver and stored in the gall bladder?
Bile is involved in digestion of lipids. Bile salts break down large droplets of lipids (emulsification) to aid lipid absorption in the small intestine.
Where does bile enter the small intestine and how does this occur?
The gall bladder releases bile into the duodenum via the common bile duct.
what structures and functions of the small and large intestine do they have in common
- peristalsis
- segmentation
- serosa
- mucosa
- musculares externa (muscular layer)
Which of the following is NOT a function of the large intestine
The digestion and absorption of lipids occurs in the small intestine.
What carries out chemical digestion in the large intestine?
bacteria (or gut biome)
