Digestive System Flashcards
What are the digestive systems accessory organs?
- teeth, tongue, salivary glands
- pancreas
- liver, gall bladder
What are the digestive processes in order?
- ingestion: food into oral cavity
- digestion: large molecule are broken down into smaller molecules, 2 types, mechanical (physical breakdown like chewing), and chemical (by enzymes and acid secretions)
- absorption: end products of digestion enter blood or lymph
- defecation: elimination of undigested material
What are the 4 basic layers of the GI tract? (from inside to outside)
- mucosa
- submucosa
- muscularis externa
- serosa
What are the layers of mucosa in the GI tract?
1) epithelium with goblet cells
- stratified squamous: mouth, pharynx, esophagus, anal canal
- simple columnar: stomach, small + large intestine, rectum
2) lamina propria (areolar CT)
- contains blood, lymph vessels, lymph nodules/tissues (immune)
3) muscularis mocosa
- smooth muscle that allows movement of mucosa
Describe the submucosa of the GI tract
- areolar CT
- contains: blood and lymphatic vessels, and submucosal nerve plexus
Describe the muscularis external of the GI tract
- smooth muscle
- inner circular layer
- outer longitudinal layer
- myenteric nerve plexus between layers
- contractions cause motility (mixing and movement)
Describe the serosa of the GI tract
- inner: areolar CT
- outer: epithelium
What is the cavity of the GI tract called
lumen
What are the structures of the digestive system?
oral cavity
salivary glands
dentition
oropharynx, laryngopharynx
esophagus
stomach
small intestine
small intestine accessory organs
large intestine
What does the oral cavity include?
- lips
- cheeks
- palate:
- hard: 2 maxillae + 2 palatine bones
- soft: skeletal muscle, posterior projection = uvula (rises to close nasopharynx when swallowing), soft if posterior to hard
- tongue:
- attached to hyoid bone, made of skeletal muscle, projections of mucosa = papillae (taste buds)
What are the salivary glands?
2 of each:
1) parotid:
- inferior + anterior to ears
- mumps: inflammation of 1 or both
2) submandibular:
- floor of mouth
3) sublingual
- below tongue on floor of mouth
What does saliva consist of?
- 99.5% water
- 0.5% solutes (enzymes)
What are primary dentition?
deciduous (“baby”) teeth (child dentition)
What are secondary dentition?
permanent teeth (adult dentition)
How many of each tooth type are in primary dentition? (in each quadrant)
central incisor: 1
lateral incisor: 1
canine: 1
premolars: 0
molars: 2
20 total in mouth
How many of each tooth type are in secondary dentition? (in each quadrant)
central incisor: 1
lateral incisor: 1
canine: 1
premolars: 2
molars: 3
32 total in mouth
Describe the crown of the tooth
- lies above the gum line
- outer layer: enamel
- acellular; highly calcified making it hard
- dentin = majority of tooth (lies deep to enamel)
Describe the neck of the tooth
- rests between crown and root
- connects the outermost layer of the crown (enamel) from the outermost layer of the root (cementum)
Describe the root of the tooth
dentin + cementum overlay
what is the difference between dentin, enamel, and cementum from bone?
bone is vascular, while dentin, enamel, and cementum is avascular
Describe the oropharynx and laryngopharynx
only muscularis external (skeletal muscle) and stratified squamous epithelium
Describe the esophagus
- passes through diaphragm to the abdominal cavity
- all 4 histo. layers in GI tract from this point on, exceptions in esophagus:
a) muscularis externa
- upper 1/3 = skeletal muscle
- middle 1/3 = skeletal + smooth muscle
- lower 1/3 = smooth muscle
b) has adventitia
- fibrous CT (no epithelium)
What are he 4 regions of the stomach?
- cardiac region (cardia): attached to esophagus
- fundus: above esophageal entrance
- body
- pyloric region (pylorus): has pyloric sphincter
What is different about the epithelial cells of the mucosa of the stomach?
epithelial cells extend down into the lamina propria, where they form columns of secretory cells called gastric glands
What are the 4 types of cells in the gastric glands of the stomach?
1) chief cells: secrete pepsinogen and gastric lipase (enzymes)
2) parietal cells: secrete HCl (pH 2)
3) G cells (enteroendocrine cells): secrete gastrin (a hormone)
4) goblet cells: (surface epithelium also contains many goblet cells)
What are rugae of the stomach?
folds of mucosa and submucosa due to contraction of muscularis mucosa which allows expansion of the stomach without tearing
Describe the muscularis external of the stomach
function: churning
3 layers:
- inner oblique
- middle circular
- outer longitudinal
What is the name of each end of the small intestine?
pyloric sphincter to ileocaecal valve
What are the 3 segments of the small intestine?
1) duodenum: first fold (short) - retroperitoneal, extra glands here secrete alkaline mucous to protect against stomach acids
2) jejunum: middle section
3) ileum: has groups of lymph nodules (peyer’s patches), they prevent infection of small intestine and bacteria from entering blood
How are the segments of the small intestine specialized to increase absorption surface area?
a) plicae circulares: submucosa is folded
b) villi: projections from mucosa into lumen
- contains: blood capillaries, and lymph capillaries (called lacteals which absorb fats)
c) microvilli: brush border on enterocytes (simple columnar) which extend into lumen
Within epithelium separate enteroendocrine cells in the stomach secrete what hormones?
secretin and cholecystokinin (CCK)
What are the small intestine accessory organs?
pancreas, liver, and gall bladder
What is the pancreas also called?
retroperitoneal
What are the 3 parts of the pancreas called?
head, body, and tail
What are the exocrine glands of the pancreas?
1) acinar cells/acini (most of pancreas)
- secrete digestive enzymes into ducts
2) duct cells (make duct walls)
- secrete alkaline fluid to neutralize stomach acid
- digestive enzymes + alkaline fluid = pancreatic juice
What are the endocrine glands of the pancreas?
1) islets of langerhans (amid acini)
- secrete hormones: insulin + glucagon to regulate blood sugar
Describe the liver
- has 4 lobes: right, left, quadrate, and caudate
- cells = hepatocytes
- filters material from GI tract (nutrients, toxins, etc) before going to rest of body
- produces bile for fate digestion
Describe the gall bladder
- muscular sac on surface of liver
- rugae, no submucosa
- store and concentrates bile between meals
What is the name of each end of the large intestine?
ileocaecal valve to anus
Describe the large intestine and what it consists of
- has no villi or folds
- consists of:
- caecum
- appendix
- colon
- ascending (right side)
- hepatic flexure
- transverse
- splenic flexure
- descending (left side)
- sigmoid
- rectum (no taeniae coli, anal canal = last 3 cm)
- anus (2 anal sphincters: internal (smooth muscle) + external (skeletal muscle, voluntary control)
What is the immune function of the lymphatic system in the intestines? Where are they found?
- lymph nodules in mucosa throughout small and large intestine
- peyer’s patches in ileum
- prevent infection of small intestine and prevent bacteria from entering blood
What is the digestive function of the lymphatic system in the intestines? Where are they found?
- lymph vessels
- most absorbed fats from small intestine enters lacteals (some into blood)
Describe the peritoneum
- serous membrane that lines the abdominal cavity
- visceral peritoneum: against organ wall
- parietal peritoneum: against abdominal cavity wall
- peritoneal cavity = filled with serous fluid
Describe the serosa between organs of the abdominal cavity
sheet of 2 fused viscera; peritoneum layer
- contains blood/lymph vessels and nerves
What are the folds of the peritoneum called?
omenta
What are the 2 omentums?
1) greater omentum
- “fatty apron”
- covers transverse colon and small intestine
- has fat for protection, insulation, and energy reserve
2) lesser omentum
- suspends stomach from liver
What is the mesentery?
- suspends small intestine from cavity wall
- double layer of parietal peritoneum
What is the retroperitoneal?
- behind the peritoneum
- peritoneum only lines 1 side
- ex: pancreas, duodenum
- anterior: parietal peritoneum
- posterior: CT (adventitia)
What is peritonitis?
inflammation of the peritoneum due to things like burst appendix or wounds
