digestive system
DESCRIPTION
DIGESTIVE SYSTEM. DIGESTIVE TRACT. Tube in which digestion occurs Also called alimentary canal, gastrointestinal tract (GI) Entire canal is about 9 meters along (30 feet) in a cadaver. Shorter in a live person. FUNCTIONS. Ingest food - PowerPoint PPT PresentationTRANSCRIPT
DIGESTIVE SYSTEM
DIGESTIVE TRACT
• Tube in which digestion occurs
• Also called alimentary canal, gastrointestinal tract (GI)
• Entire canal is about 9 meters along (30 feet) in a cadaver. Shorter in a live person
FUNCTIONS
• Ingest food
• Break down nutrients to a form that can cross plasma membranes
• Absorb nutrients
• Eliminate undigested parts
PARTS
ORAL CAVITY
• Mouth - receives food• Lips (labia) protects opening • Tongue – taste buds,
pushes food to back of throat fermium – a fold of mucous membrane that secures the tongue to the floor of the mouth
• Roof of mouth – contains made up of: 1. hard palate -anterior portion is bone 2. Soft palate posterior portion is muscle
Parts continued
• Uvula – finger-like projection that closes off nasopharynx keeps food from entering the nasal cavity
• Tonsils – protects against injection
SALIVARY GLANDS
• 3 pairs • secrete saliva• contains enzyme salivary amylase
starts digestion of starch feel flaps under tongue and cheeks – where ducts are located
• Contains substances that inhibit bacteria growth• Dissolves food chemicals so they can be tastes
• Teeth – mechanical digestion
PHARYNX – region that receives food and air
• Trachea – also called windpipe lies in front of esophagus
• Swallowing is a reflex
• Glottis – opening to the larynx
• Epiglottis – spoon shaped tissue covering a piece of cartilage covers glottis so food/liquids do not enter trachea
ESOPHAGUS
• Muscular tube
• Connects to stomach
• Remains collapsed until bolus enters
• Peristalsis – rhythmic contractions that push food along digestive tract
• No chemical digestion occurs
LAYERS OF GI TRACT
• Mucosa – inner most – moist membrane that lines the lumen
• Submucosa- beneath mucosa- made up of connective tissue, and lymph vessels
• Muscularis external - smooth muscles
• Serosa – outermost layer
Esophagus continued
• Sphincters – muscles that encircle a tube act as valves
• located at point where stomach and esophagus meet
• when open – food passes into stomach
• closed – keeps acid from entering esophagus
STOMACH
• Thick muscular wall• Wall has deep folds called rugae• Holds 4 liters when full• Stores food • Empties in 2/6 hours• Mechanical digestion – churns and mixes food with
gastric juices• pyloric sphincter connects to small intestine• Cardioesophageal sphincter – connects to esophagus
REGIONS OF STOMACH
• Fundus – expanded part of the stomach
• Body – the midportion
• Pylorus – terminal part of stomach
GASTRIC JUICES
• Pepsin – digests protein• HCL – hydrochloric acid pH 2
kills bacteria breaks down connective tissue of meat activates pepsin
• Mucus• Intrinsic factor – substance needed for the
absorption of vitamin B12 in the small intestine
MUCUS
• Thick layer of mucus • Protects stomach from HCL• Produced by goblet cells• Ulcer – open sore in wall of stomach
exposed to gastric juices bacterial infection interferes with
mucus production•
STOMACH CONTINUED
• Chyme – contents of stomach thick soupy liquid enters small intestines in small squirts
• No absorption of food occurs in stomach
• Alcohol absorption only
SMALL INTESTINE
• Major site of digestion
• Has small diameter
• About 3 meters (9 feet) long
THREE PARTS OF SMALL INTESTINE
• Duodenum – 1st part of small intestine– sphincter muscles control chyme entering – receives enzymes from liver and pancreas
• Jejunum• Ileum – terminal part of intestine
– Ends with the ileocecal valve
•
WALL OF SMALL INTESTINE
• Fingerlike projections called villi
• Microscopic microvilli absorb sugars and amino acids directly into blood stream
• Components of fats enter smooth ER where they are rejoined and enter the lacteal (small lymphatic vessels)
LARGE INTESTINE
• 1.5 Meters
• Absorbs water, salts, and vitamins
• Parts: cecum colon rectum
CECUM
• Lind end of large intestine
• Appendix – small projection may help fight infection
subject to inflammation
COLON
• Ascending
• Transverse
• Descending
• Sigmoid colon – enters rectum
RECTUM
• 20 cemeters• Anus – opening to outside
expels feces• Stretching of rectal wall sends nerve
impulses to spinal cord causing relaxation of anal sphincters
• Bacteria found in some feces produce vitamins that are reabsorbed by our body
PANCREASE
• Endocrine functions involves insulin and glucagon
• Exocrine function involves the secretion of pancreatic juices
PANCREATIC JUICES
• Sodium bicarbonate – NaHCO3
– Neutralizes chyme
• Pancreatic amylase– Digest starch
• Trypsin– Digest proteins
• Lipase– Digest fats
LIVER
• Responsible for maintaining homeostasis of blood
• Removes poisonous substances• Removes Fe and stores it• Removes Vitamins A,D,E and K and stores
them• Makes plasma proteins to maintain osmotic
pressure
LIVER CONTINUED
• Makes cholesterol and regulates amount in blood
• Maintains blood glucose levels
• Produces bile which emulsifies fat
• Produces fact
GALL BLADDER
• Sac attached to undersurface of liver
• Stores bile until needed in the duodenum
• Gall stones - cholesterol comes out of bile solution forming crystals
Feces – more or less solid product delivered to the rectum
• Resident bacteria of large intestine metabolize the remaining material
• Gases are released• Methane and hydrogen sulfide produce the
odor – more gas is produced when food is high in carbohydrates
• Bacteria make vitamin K and some B vitamins
DISEASES OF THE GI TRACT
• Acid reflux• Appendicitis• Cirrhosis• Colorectal cancer• Colostomy• Constipation• Diarrhea• Gallstones• Hemorrhoids• Hepatitis
• Hernia• IBS• Jaundice• Lactose intolerance• Mumps• Peritonitis• Ulcer• Vomiting