Anatomy test- Digestion
What is the alimentary canal?
a long, muscled tube-like structure that passes through the thoracic and abdominal cavities
Where does the alimentary canal start and end?
starts at the mouth and ends at the anus
What is the function of the alimentary canal?
digests and absorbs food and nutrients in the body
4 layers of the alimentary canal
1) mucosa
2) Submucosa
3) Muscularis
4) Serosa
Mucosa
membrane lining the alimentary canal that is made of epithelium, connective tissue, and smooth muscle
Mucosa functions
- protects tissues of the canal
- carries on secretion and absorption of dietary nutrients
- sometimes has modified folds or projections which increase surface area
Submucosa
made of loose connective tissue, housing blood and lymphatic velles, nerves and glands
Submucosa function
- nourishes surrounding layers of the alimentary canal
- its vessels transport absorbed nutrients away from digestive organs
Muscularis
muscle layer of the alimentary canal with two layers of smooth muscle
Muscularis function
propels food through the canal
Serosa
outer serous layer- visceral peritonem
Serosa function
- protects underlying tissues
- secretes serous fluid to reduce friction between abdominal organs
How does the process of digestion start in the mouth?
mechanical digestion- teeth chew the food into smaller pieces and the tongue moves and mixes them with saliva rolling them into a bolus
What is enzyme amylase responsible for breaking down?
breaks down carbs into glucose
Where is the first place amylase is produced
salivary glands and in saliva
What other organ in the digestive system produces amylase?
the pancreas
What is a bolus?
mixture of food particles and saliva rolled by the tongue
Peristalsis
wavelike contractions that keep food moving in one direction through the alimentary canal
Functions of the stomach
receives food with gastric juice, initiates protein digestion using pepsin enzymes, carries on limited absorption, and moves food into the small intestine
What does hydrochloric acid do?
- activates pepsin
- helps absorb B12
- destroys pathogens
Function of Liver
- Produces, stores, and releases bile
- absorbs nutrients from the small intestine
- removes harmful substances from the digestive tract.
Function of the gallbladder
stores and concentrates bile
Function of bile
- Bile contains bile salts, which break down large fat molecules (using pancreatic lipase) into smaller ones
- elimination of certain waste products
What are the three regions of the small intestine?
1. Duodenum
2. Jejunum
3. Ileum
What happens in the Duodenum of the small intestine?
- sodium bicarbonate neutralizes the acidic chyme
- enzymes from the pancreas start to break down nutrients: pancreatic amylase, pancreatic lipase, and protease
- bile is released into the duodenum and the bile salts break down fats into smaller droplets
What happens in the Jejunum of the small intestine?
- Enzymes produced by the cells lining the jejunum's walls break down complex nutrients into simpler molecules.
- absorption of nutrients and water diffused into the blood stream
What happens in Ileum of the small intestine?
- absorption of nutrients, particularly vitamin B12, bile salts, and whatever remains of nutrients not absorbed in the jejunum
What are the intestinal villi?
- tiny projections of mucous membrane on the inner layer of the small intestine
- each consists of columnar epithelium and a core of connective tissues
What is the purpose of intestinal villi?
· Increases surface
· Aids in absorption of digestive products
What substances are secreted or produced in the small intestine?
- enzymes maltase, sucrase, lactase, peptidases, and lipase.
- bile, from the liver and gallbladder
- mucous, from globlet cells
- sodium bicarbonate
What are the functions of the large intestine?
- absorb water and electrolytes
- stores fecal matter until it is ready to be expelled from the body
- forms feces from the remaining waste after the water is absorbed
- maintaining a resident population of over 500 species of bacteria
- bacterial fermentation of indigestible materials.
What is haustra?
pouch-like structures that help the large intestine expand and contract, aiding in the absorption of water and electrolytes from waste material.
What is the microbiome?
diverse community of microorganisms that inhabit the digestive tract
What are the parts of the large intestine?
- Cecum- start
- Appendix- irrelevant
- Ascending- goes up
- transverse- longest
- Descending- goes down
- sigmoid
- rectum
-anal canal- leads to anus
what is in a single villus?
- contains a network of blood vessels and a lacteal (lymphatic vessel) surrounded by epithelial cells
what do epithieal cells have on them?
have microvilli on their surface, increasing the surface area available for absorption of nutrients.
Where does carb digestion start and end?
starts in the mouth and ends in the small intestine
What are the 3 accessory organs?
Liver, gall bladder, and pancreas
Where are most of the enzymes produced?
pancreas
Function of the epigollotis
close the trachea and force the bolus down the esophagus
What happens to nutrients after absorbed into the blood?
Transported to the cells in the body
Chemical digestion
the breaking down of molecules using enzymes
Where does the breakdown of proteins start and finish?
starts in the stomach and finishes in the small intestine
Where does the breakdown of fats start and finish?
they start and finish in the first part of the small intestine
Mechanical digestion
breaking down of bigger food pieces into smaller pieces
Rugae
large folds that allow the stomach to expand and contract
What are carbs digested into and used for?
glucose, and used for quick and long-term energy
What are proteins digested into and used for?
Amino Acids and used to build our bodies
what are Fats (triglycerides) digested into and used for?
fatty acids and glycerol, which are used for energy