Topic 15: Digestive System Flashcards
What does the digestive system include?
1) Gastrointestinal (GI) tract
2) Accessory organs
Gastrointestinal (GI) tract
tube from mouth to anus
Accessory organs
teeth, tongue, salivary glands
pancreas
liver, gall bladder
List the digestive system processes:
1) Ingestion
2) Digestion
3) Absorption
4) Defecation
Ingestion
food into oral cavity ←
secretion right away (occur throughout entire system)
Digestion
large molecules broken down into smaller molecules
List the 2 types of Digestion
a) mechanical
physical breakdown & motility
e.g. chewing
b) chemical
enzymes + acid secretions - ) salivation
what is the main purpose of the stomach?
storage= can remove it and person will still be alive
Absorption
# 1 goal (want carbs etc ) end products of digestion enter blood or lymph
Defecation
elimination of undigested material
List the 4 basic layers of the GI tract
1) Mucosa
2) Submucosa
3) Muscularis Externa
4) Serosa (or adventitia)
List the layers of the mucosa
a) epithelium with numerous goblet cells
stratified squamous: mouth, pharynx, esophagus, anal canal
simple columnar: stomach, small + large intestines, rectum
b) lamina propria = areolar CT
contains blood, lymph vessels, lymph nodules/tissues (immune)
c) muscularis mucosa
smooth muscle - allows movement of mucosa
Submucosa
areolar CT
contains: blood + lymphatic vessels, submucosal nerve plexus
Muscularis Externa
smooth muscle inner circular layer outer longitudinal layer myenteric nerve plexus between layers contractions cause motility (mixing + movement)
What does the oral cavity include?
a) lips
b) cheeks
c) palate
d) tongue
hard palate
2 maxillae + 2 palatine bones
soft palate
(posterior to hard palate) skeletal muscle
posterior projection = uvula
rises to close the nasopharynx when swallowing
tongue
skeletal muscle
projections of mucosa = papillae (taste buds)
- attcahed to hyoid bone
List the Salivary Glands:
parotid
inferior and anterior to ears
mumps = inflammation of 1 or both parotids
submandibular
floor of mouth
sublingual
below tongue on floor of mouth
saliva
- 5% water
0. 5% solutes (e.g. enzymes)
Dentition (teeth):
in maxillae and mandible
child dentition
o primary dentition
- deciduous teeth
adult dentition
secondary dentition
permanent teeth
How many total teeth do adults have vs children?
adults= 32 children= 20
crown
above the gum
dentin = majority of tooth
enamel overlay = acellular, highly calcified hard!
- bacteria wear it down =
cavity
root
dentin + cementum overlay
NOTE: dentin, enamel, & cementum
similar to bone, but avascular
List the how many of each tooth children have
central incisor: 1 lateral incisor: 1 canine: 1 Premolar:0 molar: 2 x 4 each
List the how many of each tooth adults have
central incisor: 1 lateral incisor: 1 canine: 1 Premolar:2 molar: 3 x 4 each
neck
enamel + cementum boundary (gums)
periodontal ligaments
attach root to bones
root canal extends to pulp cavity
contains CT, blood/lymph vessels, and nerves
Oropharynx and Laryngopharynx:
only muscularis externa (skeletal muscle) and stratifIied squamous
Esophagus:
posterior to trachea
passes through diaphragm to the abdominal cavity
all 4 histological layers in GI tract from this point on
What are the exceptions in esophagus in regards to histology?
a) muscularis externa
upper 1/3 = skeletal muscle
middle 1/3 = skeletal + smooth muscle
lower 1/3 = smooth muscle
b) has adventitia
= fibrous connective tissue (no epithelium)
List the regions of the stomach
a) cardiac region (cardia):
attached to esophagus
b) fundus
above esophageal entrance
c) body
d) pyloric region (pylorus)
has pyloric sphincter
Stomach function
has greater and lesser curvatures
converts food into chyme (= food + gastric juice)
describe the stomach mucosa
o invagination of epithelium forms gastric glands (exocrine) secrete gastric juice to lumen
what do gastric glands contain
a) chief cells
secrete pepsinogen (inactive form of pepsin) + gastric lipase (enzymes)
b) parietal cells
secrete HCl (pH 2)
c) G cells (enteroendocrine cells)
secrete gastrin (hormone)
d) Goblet cells (surface epithelium also contains many goblet cells)
rugae
folds of the mucosa + submucosa due to contraction of muscularis mucosa
o allows expansion of stomach without tearing
describe the muscularis externa of stomach
o function = churning o 3 layers: a) inner oblique b) middle circular c) outer longitudinal
Small Intestine:
pyloric sphincter to ileocaecal valve
Describe the segments of the small intestine
a) duodenum first fold (short) retroperitoneal extra glands here secrete alkaline mucous to protect against stomach acid (neutralize stomach acid = not cause damage t o S I
b) jejunum
middle section
c) ileum
attached to caecum (part of large intestine)
- has group of lymph nodules= peyer’s patches
peyer’s patches
group of lymph nodules
- prevent infection of sm int. and bacteria from entering blood
What are the segments in SI specialized for?
to increase absorption surface area
a) plicae circulares- submucosa thrown into folds
b) villi- projections of mucosa into lumen
contains:
o blood capillaries
o lacteals (= lymph capillaries that absorb fats)
c) microvilli- brush border on enterocytes (simple columnar)
- extend into lumen
within epithelium separate enteroendocrine cells secrete the hormones: o secretin o cholecystokinin (CCK)
List the SI acessory organs
a. pancreas
b. liver
c. gall bladder
Pancreas
retroperitoneal
parts: head, body tail
what is the largest gland in the body
liver
Liver
4 lobes: o right, left , quadrate, caudate cells = hepatocytes; hepa = liver filters material from GI tract (nutrients, toxins, etc.) before going to rest of body produces bile for fat digestion
Gall Bladder
muscular sac on surface of liver
rugae, no submucosa
stores and concentrates bile between meals
Large Intestine:
ileocaecal valve to anus
no villi or folds
What does the large intestine consist of?
a) caecum
b) appendix
c) colon
d) rectum
e) anus
list the parts of the colon
i. ascending (right side)
ii. hepatic flexure
iii. transverse
iv. splenic flexure
v. descending (left side)
vi. sigmoid
muscularis externa longitudinal layer incomplete = taeniae coli o contraction forms pouches = haustra
epiploic appendages = fat filled pouches o function unknown
rectum
no taeniae coli
anal canal = last 3 cm
anus
2 anal sphincters: internal (smooth muscle) + external (skeletal muslce voluntary control)
Immune function:
lymph nodules in mucosa throughout small + large intestine Peyers patches in ileum
o prevent infection of small intestine and prevent bacteria from entering blood
Describe the function of the lymphatic system in the intestines
1) Immune function:
2) Digestive function:
2) Digestive function:
lymph vessels
o most absorbed fats from small intestine enters lacteals (some into blood)
Portal System
blood vessels between 2 capillary beds ( but blood doesn’t pass through the heart between them)
peritoneum
abdomen
serous membrane
o visceral peritoneum (against organ wall)
o parietal peritoneum (against abdominal cavity wall)
o peritoneal cavity = filled with serous fluid
serosa between organ
= sheet of 2 fused visceral peritoneum layers o contains blood/lymph vessels + nerves
omenta:
forms folds in some areas
greater vs lesser
1) greater omentum
“fatty apron”
covers transverse colon + sm. int.
has fat - protection, insulation, energy reserve
2) lesser omentum
liver to stomach
mesentery
suspends small intestine from cavity wall
double layer of parietal peritoneum
retroperitoneal
o behind the peritoneum o peritoneum lines only one side e.g. pancreas, duodenum o anterior = parietal peritoneum o posterior = CT (adventitia)
peritonitis
- inflammation of the peritoneum
- due to burst appendix wounds
