Digestive System P.5 Aaliyah Avina
Major Functions of the Digestive System
- Digestion (breakdown) and absorption of food from metabolism (energy and growth an repair of tissues)
- Mechanical & Chemical digestion
- Excretes food components that are indigestible
- Digestion- the breakdown of food into smaller molecules
Major Organs of the Digestive System
Alimentary Canal (GI Tract)
- Absorption- chemically digested food moves from intestine into blood & lymph
Mouth
-A long irrgegularly shaped tube at both ends (30ft long)
-Digests food & absorbs the building
-recieves food and begins mechanical digestion by mastication
-chemical digestion also occurs
-saliva=enzymes
-food is moved towards (bolus) to pharynx
Anterior opening= oral office
Pharynx "throat"
-Is the passageway for food (& air) from mouth to esophagus
-Has 3 part; Nasopharynx, Oropharynx, Laryngopharynx
-recieves food from mouth
Esophagus
-A passageway leading to stomach through a diaphragm opening. (only for food)
-connects pharynx to stomach
-moves food (bolus) by peristalsis
Peristalsis= rhythmic wavelike contraction by muscularis layer of wall
-Connects to stomach at lower esophageal (cardiac) sphincter
Stomach
-J shaped, can hold 1 L +
3 PARTS:
- Cardia & the Fundus- enlarged opening next to esophagus (upper section)
- Body- central main part
- Pylorus (pyloric)- lower narrow section
-mixing & holding chamber, chemical & also mechanical digestion
-very little absorption
Small Intestine
-22 ft long
-connects stomach to large intestine
-breaks down food from the stomach & absorbs much of nutrients from food
3 SECTIONS:
- Duodenum- most fixed in place
- Jejunum- absorption
- Ilium- absorbs vitamins & bile salts
-Ileoceacal sphincter (valve) joins small to large intestines cecum
Large Intestines
-Digestion by bacteria
-Absorption of water & salt
-Form, store, eliminates feces
-5ft long, wider
SUBDIVISIONS
- Cecum
- Ascending
3.Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal (Anus)
Accessory Digestive Organs
Teeth
-Masticate (chew) food into smaller pieces
-Mechanical breakdown of food
4 TYPES:
- Incisors- cut
- Canines (cuspid)- tear & shred
- Premolars (bicuspid) - crush & grind
- Molars- crush & grind
Structure= crown, neck, root
Tongue
-thick muscular organ covered by mucus
-moves & mixes food with saliva
-Food + saliva = bolus
-Taste receptors
Liver
-Largest internal organ
-Regulates most chemical levels in the blood & excretes bile into duodenum
-converts carbohydrates & proteins to fats
-Responsible for many metabolic activities
Gall Bladder
-stores bile for liver
-is under surface of the liver
-concentrates & stores bile produced in the liver, to release into small intestine (duodenum)
Salivary Glands
-secrete saliva
-contains serous cells that produce a watery fluid w/ salivary amylase (enzyme)
-they recieve parasympathetic -> triggers production of a large volume of saliva @ sight / smell of food
Pancreas
-Parotoid glands- front of ear, secrete clear, serous in amylase
-Submandibular glands- on floor mouth, secrete more viscous fluid
-Sublingual glands- inferior to tongue, secrete saliva that is thick & stringy (mucous)
-is behind stomach
-secretes pancreatic juice (made by pancreatic acinar cells) into duodenum
-enzymes to digest nutrients:
protease, trypsin, lipase, amylase
Digestive Enzymes
Pepsin (Peptidases)- stomach enzyme, serves to digest proteins found in ingested food
Sucrase- aids in breakdown into glucose & fructose, used as body fuel
Lactase- breaks down into smaller sugar called glucose & galactose
Maltase- produces simple sugar glucose
Amylase- polysaccharides into discchardies & monossaccharides
Location of Digestion & Absorption of each Macromolecule
Carbohydrates
Layers of GI Tract
⭐ Most inner layer layer to the exterior ⭐
Disorders of the Digestive System
-the digestion of them begin in mouth w/ the mechanical action of chewing
-they then travel to the exophagus to you stomach
-most carbohydrates digestion occurs in the small intestine.
-by end were left off with glucose, fructose and galactose , where they can now be absorbed
Protein
-digestion & absorption of proteins mostly occurs in small intestine
-chyme leaves the stomach & enters small intestine
Protein-> peptidases-> amino acids
-begins in stomach chemical digestion, turn protein into smaller polypeptides
-broken down by salivary & pancreatic amylse
Nucleic Acid
nucleic acid-> nucleases -> nucleotides
-digested in small intestine w/ help of pancreatic enzyme & enzyme produced by small intestine
-absorption mainly occurs in duodenum & jejunum
1. Mucosa
-produces mucus for reduction of friction & protections
Has 3 layers:
Epithelium- protection against friction, in mouth, esophagus and anus( stratified squamous)
-is simple columnar in intestine for absorption & secretion
Lamina propria- areolar ct, has blood & lymphatic vessels & lymph node for nourishment & immunity
Muscularis mucosae- 2 thin layer of smooth muscles
2. Submucosa
-Areolar ct containing major blood vessel
-Many elastic fibers to retain shape
-Submucosal plexus, autonomic nerve supply
-glands & lymphatic tissue
3. Muscularis Layer
-muscle layer
-2 layers of smooth muscles to allow peristalsis & segmentation
Inner circular layer- squeeze, decreases size of lumen , some areas acts as sphincter / valves
Outer longitudinal layer- shortens intestine
myenteric plexus -nerves
4. Serosa
-Outer covering of the GI tract
-serous membrane, had thin layer of areolar ct & simple squamous epithelium
-produces serous fluid for lubrication
-covers the outside of abdominal organs
-attaches the digestive tract to wall of the abdominopelvic cavity by forming folds called mesenteries
Gallstones- blocks bile duct
-obstruction of common hepatic duct
Jaundice- yellow skin discoloration due to excessive amounts of bile of blood
-various causes (gallstones, diseased liver, hepatitis)
Hepatitis- an inflammation of the liver
-drug toxicity & wild mushroom poising
-due to six hepatitis viruses
Cirrhosis- chronic inflammation of the liver resulting alcoholism, or chronic hepatitis
-transplant at the end of the liver