Download Digestive system

Digestive system
Digestive System Functions
•_______________________: occurs when materials enter digestive tract via the mouth
•Mechanical processing: ___________ and shearing; makes materials easier to propel along digestive tract
•________________: is the chemical breakdown of food into small organic fragments for absorption by
digestive epithelium
•________________: is the release of water, acids, enzymes, buffers, and salts by epithelium of digestive tract
by glandular organs
•___________________: movement of organic substrates, electrolytes, vitamins, and water across digestive
epithelium into interstitial fluid of digestive tract
•______________________: removal of waste products from body fluids
Alimentary Canal
•a hollow tube extending from ____________ to __________________
•Four main tissue layers
1.
2.
3.
4.
•Foods must be broken down to their building blocks to be absorbed.
–_______________ building blocks: simple sugars
–Protein building blocks: _______________________
–Fat or lipid building blocks: fatty acids and glycerol
Oral cavity
Functions of Oral Cavity
•___________________: mixing with mucus and salivary gland secretions
•Limited digestion of _______________________ and ___________________
•Sensory analysis of material before swallowing
•Mechanical processing through actions of teeth, tongue, and palatal surfaces
Tongue
Salivary Glands
•Three pairs – parotid, submandibular, and _____________________
•Secrete saliva into the oral cavity
•Contains _________________ and serous fluids
•The serous component contains salivary ___________________
Teeth
•Two sets of teeth are formed.
•The first set consists of ____ deciduous teeth that begin to appear at 6 months of age and are lost by 12 years.
•Permanent teeth (____________) begin to replace deciduous teeth around 7 years.
•A typical tooth consists of crown covered with enamel and root covered with ______________________.
•Most of the tooth is bonelike ______________________.
•The _______________________ contains blood vessels and nerves
Types of Teeth
•_______________________ – thin, sharp teeth that are best for cutting ( 8 total)
•Canines – teeth that aid in tearing ( 4 total)
•Premolars – __________________ food ( 8 total)
•Molars – larger and also used for grinding (12 total)
Mastication: Also called _______________________
•As you chew your food it mixes with saliva and becomes a round ball called a _____________.
Pharynx
•The pharynx is a muscular tube that provides passage way for both ____________ and air.
•Regions of the Pharynx
–Nasopharynx
–Oropharynx
–Laryngopharynx
•Food passes through __________________________ and laryngopharynx to esophagus
Swallowing
•Swallowing has two phases:
–The ________________ phase
•voluntary
•begins in the mouth
•the tongue pushes the bolus into the pharynx
–pharyngeal-esophageal phase
•involves the closing off of nasal and respiratory passages
•conduction of food to the stomach by ____________________ from the pharynx through the esophagus
Peristalsis
Esophagus
•A hollow ___________________ tube
•About 25 cm long and 2 cm wide
•Conveys solid food and liquids to the stomach
•Begins posterior to ___________________ cartilage
Stomach
Functions of the Stomach
•__________________ of ingested food
•Mechanical breakdown of ingested food
•Disruption of ______________________ bonds in food material by acids and enzymes
•Production of ____________________ factor: glycoprotein required for absorption of vitamin B12 in small
intestine
Regions of the Stomach
Cardia, Fundus, Body, pylorus
Parts of the stomach
Stomach Anatomy
•C-shaped organ
•located on the left side of the abdomen beneath the diaphragm.
•Food enters it through the _____________________________ sphincter
•Food leaves to enter the small intestine through the _______________________ sphincter.
4 Layers of the Stomach
•Serous Coat: covers most of the stomach
•Muscular Coat: churns food, three layers of muscles that run in different directions
•Mucous Coat: protects the inner lining of the stomach
•Submucosal Coat: connects the muscular and mucosal layers
Stomach Layers
Mechanical Digestion
•3 layers of muscularis layer
–Longitudinal
–Circular
–Oblique
•3 layers allow churning and mixing of food (______________________ digestion)
What happens in the stomach?
•Food enters and gastric secretions is stimulated by the ______________ nerves and by _______________
•____________________ activates the protein digesting enzyme pepsin
•Food is mechanically broken down by _______________________ of stomach muscles
Mucous Coat of Stomach
•Mucous cells secrete mucous that protect the cells lining the stomach and prevent the stomach from digesting
itself.
•When the stomach is empty, the walls are folded into __________________ (stomach folds), which allow the
stomach to expand as more food fills it.
Stomach Digestion
•________________________ contractions (mechanical digestion) mix the bolus with strong digestive juices
that the stomach lining cells secrete (____________________ digestion)
Stomach - Chemical Digestion
Carbohydrate digestion continues in the stomach.
•Protein digestion begins in the stomach.
–_______________________ and HCL are secreted into the lumen of the stomach
–HCL converts pepsinogen to _____________________ and contributes to the breakdown of the bolus
into a liquid called _____________________.
–Pepsin begins the ______________________ digestion of proteins.
Stomach
•Stomach has stretch receptors to indicate to the brain when stomach is full.
•Food is digested in the stomach for several hours.
•Chyme is slowly transported from the ____________________ (end of the stomach) through the pyloric
sphincter into the small intestine.
Stomach to small intestine
•Food moves through the pyloric sphincter into the small intestine
•Chyme – name given the partially digested food that moves into the SI from the stomach.
Small Intestine
•Tube-like suspended from the posterior body wall by the mesentery
•21 feet long
•Begins at the pyloric sphincter and ends at the ____________________
•Food digestion and ____________________________ are completed here
3 Parts of the small intestine
•The small intestine is subdivided into the ________________, ____________________, and ___________.
Intestinal Movement
•SI moves food by _______________________ and mixes it by _______________________
•________________ propels food through the intestine by waves
•Segmentation mixes food by sequential movement.
Duodenum
•The first portion of the small intestine is the duodenum where acidic chyme from the stomach mixes with bile
from the liver & gallbladder and digestive juices from the pancreas & intestine itself.
Small Intestine: Chemical Digestion:
The pancreas and gland cells of the small intestine secrete digestive enzymes. Enzymes include
–________________: protein digestion
–Amylase: ____________________ digestion
–Lipase: ___________________ digestion
•_______________________ is created in the liver and stored in the gallbladder.
–emulsifies (breaks down) lipids (fats)
•like dish detergent with grease
Pancreas
•Secretion of pancreatic juice into the ________________________
•Pancreatic juice contains enzymes that digest carbs, fats, proteins, and nucleic acids
Liver
•Largest internal organ
•Liver is divided into two lobes
•Secretes a digestive fluid called _____________, produced by the breakdown of dietary fats and old red blood
cells
•Removes _________________ and wastes from the blood
Gall Bladder
•Pear shaped sac on the inferior surface of the liver
•_____________________ bile from the liver
Digestion Ends - Once food passes through the duodenum, digestion is complete.
Small Intestine: Jejunum and Ileum
•Chyme then passes into the jejunum and ileum.
Surface of Small Intestine
•Surface contains lymph vessels and small arteries and veins
•Millions of projections called _____________ increase _________________ which aids in absorption of
nutrients
Food Absorption
•Food molecules enter the bloodstream through intestinal walls
•Capillaries absorb proteins and carbohydrates
•Lymph vessels absorb products of fat digestion that eventually lead to the bloodstream
Wall of Small Intestine
Intestinal villi
Large Intestine
•Once food has passed through the small intestine it is mostly __________________ material and water.
•Food now enters the large intestine
Large Intestine 6 parts
Cecum Ascending colon Transverse colonDescending colonSigmoid colonRectum
Colon
Cecum
•Pouch shaped beginning of the colon
•____________________ is attached to the bottom of the cecum
•Appendix intercepts pathogenic microorganisms and sometimes fecal matter
Large Intestine
•The rest of the large intestine absorbs water and turns chyme into _____________________
Rectum
•Final section of the large intestine
•Empty except just before and during defecation
Anus
•Contain ______________________ sphincters which act as valves during defecation
Disorders of the Digestive System
Hernia - A ________________ of an organ or body tissue out of the body cavity that it normally occupies.
Peptic Ulcer - Areas of eroded tissue in the lining of the stomach, esophagus, or duodenum
Liver Disease - Cirrhosis – scarring of the liver from ____________________ abuse
Hepatitis - Inflammation of the liver
Gallstones- Solid accumulation of _______________ pigment and cholesterol
Cancer - Pancreatic and colon cancer
Hemorrhoids - Swollen ______________ in the lining of the anus; can be internal or external
Nutrition
Nutrients: Chemical substances supplied from the environment that an organism requires for survival
Metabolism: All chemical breakdown (catabolic) and building reactions (anabolic) needed to maintain life
Sources of major nutrients
 Carbohydrates
Organic compounds which include sugars and starches
One of the body’s main sources of _____________________
 Lipids
Organic compounds that include fats, oils, and fatlike substances.
The body’s other main source of energy
 Proteins
Long chains of _____________________ that help with cell growth and repair
 Vitamins
Organic compounds required in small amounts.
Fat-soluble vitamins are ________________________________Water-soluble vitamins are B and C
 Minerals
Inorganic elements that are essential in human metabolism.
Most concentrated in bones and teeth and make up about _______________ of our body weight