Digestive System Flashcards
Mechanisms
Ingestion-taking in food
Digestion-break nutrients into smaller (mech. and chem.)
Motility-movement of muscles (peristalsis and segmentation)
Secretion-release of dig. juices to facilitate digestion
Absorption-movement of digested materials into body
Elimination-ridding body of waster material
Regulation-coordination of dig. activity
Overview
- gastrointestinal (GI) tract
- aka alimentary canal
- 9m long
- not truly part of the body
- extends from mouth to anus
Walls of GI Tract
-lumen-hollow space w/in tube
1) Mucosa
- innermost, varies organ to organ
- esophagus tough, rest delicate for absorption
2) Submucosa
- connective tissue
- contains blood vessels and nerves
3) Muscularis
- 2 layers of muscle tissue
- produce movement
4) Serosa
- outermost
- anchored to ab. cavity wall by mesentary
Oral Cavity
- hollow chamber with roof, floor, walls and lined with mucous membrane
- hard palate-roof of mouth, bony structure
- soft palate
- rear portion, mostly muscle
- Uvula hangs from center
- prevents food/liquid from entering nasal cavity
Tongue
- muscle covered with mucous membrane
- anchored to bones in skull and hyoid bone in neck
- frenulum attached tongue to floor
- divided into root, tip, body
Tooth
Crown
- exposed and visible
- covered by enamel (hardest tissue in body)
- dentin forms majority of tooth
- dental caries occur in dentin, enamel
Neck
- narrow section, joins crown to root
- surrounded by gingiva (gum) tissue
Root
-fits into bony socket
- Deciduous (baby)–>20
- Permanent –>32
Salivary Glands
Serous Secretions
- thin, watery, free of mucus
- contain salivary amylase (carb dig.)
Mucus Secretions
- thick and slippery
- lubricates food
Parotid
- largest, below and in front of each ear
- serous secretions
Submandibular
- both serous and mucous
- open into mouth beside frenulum
Sublingual
- in front of submandibular
- mucus secretion
Pharynx
- tube-like structure
- muscle and mucous membrane
- 3 parts
1) Nasopharynx
2) Oropharynx
- most directly involved in digestion
- involved in swallowing (deglutition)
3) laryngopharynx
Esophagus
- muscular, mucus-lined tube
- connect pharynx with stomach
- passageway for food
- 25cm
Stomach
- pouch that food enters
- size of large sausage, expands considerably
Walls
- 3 smooth muscle layers make up muscularis layer
- contractions result in peristalsis
- mucous membrane lines stomach
- gastric glands secreting gastric juice and HCl
- when empty, lies in folds (rugae)
3 divisions
1) Fundus-enlarged portion, L of esophagus
2) Body-central portion
3) Pylorus-lower narrow section joining with sm. int.
- pyloric sphincter (b/w stomach and sm. int.)
LES (Lower Esophageal Sphincter)
- aka cardiac sphincter
- prevents food from re-entering esophagus
- ring of muscle tissue
Chyme
- semisolid mixture
- food mixed with gastric juice
- continuation of mechanical digestion
Small Intestine
-about 7m
Duodenum
- C-shaped
- chemical digestion occurs here
- pancreatic and liver ducts open here
Jejunum, Illeum
Mucous Lining
- 1000s of int. glands secrete digestive juice
- arranged in multiple circular folds (plicae)
- folds covered with villi with capillaries
- each villus has lacteal (absorbs fat from chyme)
- creates more SA for absorption
Liver
- large, fills upper right section of abdomen
- exocrine gland
- secretes bile which emulsifies fats
- hepatic ducts drain bile out of liver
- Bile–>mechanism for secreting cholesterol
Gallbladder
- concentrates and stores bile produced in liver
- contraction stimulated by release of cholecystokinin (CCK, a hormone)
- CCK stim. by chyme containing fat entering duodenum
Pancreas
- exocrine–>secretes pancreatic juice into ducts
- endocrine–>secretes hormones into blood
- enters small intestine at same place as bile
- lies behind stomach
Pancreatic Juice
- most important dig. juice
- contains enzymes to digest all 3 foods
- contains sodium bicarbonate to neutralize Hydrochloric acid
