Function of Digestive System
Is a tube running from the mouth to the anus. It's chief goal is to break down huge proteins, fats, & starch (macromolecules), which cannot be absorbed intact, into smaller molecules (amino acids, fatty acids & glucose) that can be absorbed across the wall of the tube & into the circulatory system for dissemination throughout the body. Each cell takes the nutrients it needs.
2 regions of Digestive System
Alimentary Tract/Canal & Accessory Organs
Mouth, Pharynx & Esophagus, Stomach, Small & Large Intestines, Rectum & Anus
Tongue, Teeth, Liver, Gallbladder, Pancreas
Foods are broken down mechanically by chewing & saliva is added as a lubricant. In some species saliva contains amylase which is an enzyme the digests starch.
has a cleansing action on the teeth, moistens & lubircates food during mastication & swallowing, dissolves certain molecules so food can be tasted & it begins the chemical digestion of starches through the action of amylase which breaks down polysaccharides & disaccharides.
a simple conduit between the mouth & stomach. (basically a slip n slide)
enzymatic digestion of proteins initiated & foods are reduced to liquid form called Chyme. It receives food from the esophagus & is located in the upper left quadrant of the abdomen. It is a "J" shaped organ.
is the center of metabolic activity in the body. it's major role in digestion is to provide Bile Salts to the small intestine (critical for digestion & absorption of fats)
Secretion, synthesis of Bile Salts, synthesis of Plasma Protein, Storage, Detoxification, Excretion, Carbohydrate Metabolism, Lipid Metabolism, Protein Metabolism, Filtering
is a pear shaped sac that is attached to the visceral surface of the liver by a cystic duct. Main function is to serve as a storage reservoir for bile.
is a yellowish-green fluid produced by the liver cells. The main components are water, bile salts, bile pigments & cholesterol
act as emulsifying agents in digestion & absorption of fats (it breaks them down then absorbs). Cholesterol & Bile Pigments from the breakdown of Hemoglobin are excreted from the body in bile.
has important roles as both an endocrine & exocrine organ. It provides a potent mixture of digestive enzymes to the small intestine which are critical for digestion of fats, carbohydrates & protein. Enzymes include: Amylase, Trypsin, Peptidase & Lipase. Secretions are controlled by the hormone Secretin.
breaks down protein
breaks down protein
breaks down fat
breaks down carbohydrates
where the final stages of chemical enzymatic digestion occurs and almost ALL nutrients are absorbed. Has 3 sections (in descending order): Duodenum, Jejunum, Ileaum.
Small Intestine Sections
Duodenum, Jejunum, Ileaum....this is where most of absorption happens (descending order)
water & electrolytes are absorbed, bacterial fermentation takes place and feces is formed for elimination. It consists of: Colon, Rectum & Anal Canal.
from the Signoid Colon to the Anal Canal & has a thick muscular layer. It follows the curvature of the Sacrum & is firmly attached to it by connective tissue. It ends about 5 cm below the tip of the coccyx @ the beginning of the anal canal
the last 2-3 cm of the digestive tract which continues from the rectum and opens to the outside at the anus. The mucosa of the rectum is folded to form longitudinal anal columns. The smooth muscle layer is thick and forms the internal anal sphincter at the superior end of the anal canal and is under involuntary control. The external anal sphincter at the inferior end is made up of skeletal muscle and is under voluntary control.
Intestinal Wall Anatomy
a long continuous tube that is the digestive tract & about 9 meters in length. It opens to the outside at both ends (mouth & anus). The basic structure of the wall is the same throughout the entire length of the tube. It has 4 layers (tunics): Mucosa, Submucosa, Muscular Layer (smooth), Serous layer (serosa)
is the inner most tunic of the wall. It lines the lumen of the tract/canal. It consists of epithelium, an underlying loose connective tissue, and a thin layer of smooth muscle called Muscularis Mucosa. In certain areas it develops folds that increase the surface area. Certain cells secrete mucus, digestive enzymes & hormones. Ducts from other glands pass through to the lumen. In the mouth and anus the epithelium is stratified squamous tissue for protection from abrasion. The stomach and intestines have thin simple columnar epithelial layer for secretion and absorption.
is a thick layer of loose connective tissue that surrounds the mucosa. It contains blood vessels, lymphatic vessels & nerves. Glands may also be embedded in the layer.
is responsible for the movements of the digestive tract/canal
secretes serous fluid for lubrication so organs move smoothly against each other without friction.