Topic 15 -Digestive System Flashcards
The digestive system includes 2 parts
Gastrointestinal (GI) Tract -tube from mouth to anus
Accessory Organs
- teeth, tongue, salivary glands
- Pancreas
- liver, gallbladder
what are the 4 points of the digestive system processes
Ingestion
Digestion
Absorption
Defecation
Ingestion
food into oral cavity
Digestion
large molecules broken down into smaller molecules
2 types mechanical (chewing) and chemical (enzymes + acid secretion)
Absorption
end products of digestion enter blood or lymph
Defecation
elimination of waste + undigested material
what are the 4 basic layers of the gastrointestinal tract
Mucosa
Submucosa
Muscularis externa
Serosa (adventitia)
cavity=lumen
Mucosa of the GI tract (3 layers)
epithelium with numerous goblet cells
- stratified squamous: mouth, pharynx, esophagus, anal canal
- simple columnar: stomach, small + large intestine
lamina propria=areolar CT
-contains blood, lymph vessels, lymph nodules/tissues (immune)
muscularis mucosa
-smooth muscle -allows movement of the mucosa
submucosa of GI tract
areolar CT
contains: blood and lymphatic vessels, submucosal nerve plexus
Muscularis externa of GI tract
- smooth muscle
- inner circular layer
- outer longitudinal layer
- myenterric nerve plexus between layers
- contractions cause motility (mixing +movements)
Enteric Nervous system
what controls the muscularis externa
what controls the activity of the mucosal glands and muscle
Nervous system of GI Tract
myenteric plexus -controls muscularis externa
submucous plexus -controls activity of mucosal glands and muscle
what does the Oral Cavity include
lips
cheeks
palate:
hard palate= 2 maxillae and 2 palatine bones
soft plate -posterior to hard -skeletal muscle
-posterior projection= uvula
-rises to close the nasalpharynx when swallowing
tongue:
-attached to hyoid bone
-skeletal muscle
-projections of mucosa=papillae (taste buds)
Salivary Glands (3 pairs)
parotid -inferior and anterior to ears
submandibular -floor of mouth
sublingual -below tongue on floor of mouth
mumps
inflammation of 1 or both parotids
saliva
- 5% H2O
0. 5% solutes (enzymes)
Dentition (teeth) -where are they located
-in maxillae and mandible
child dentition
primary (1°) dentition -decidous (“baby”) teeth
adult dentition
secondary (2°) dentition -permanent teeth
number of central Incisors per quadrant
child 1
adult 1
number of lateral incisors per quadrant
child 1
adult 1
number of canine per quadrant
child 1
adult 1
number of premolars per quadrant
child 0
adult 2
number of molars per quadrant
child 2
adult 3
total teeth and total per quadrant
child 20 teeth 4 per quadrant
adult 32 teeth 8 per quadrant
Tooth structure (parts)
crown root neck periodontal ligaments root canal extends to pulp cavity
crown of tooth what does it contain
above gum
dentin=majority of tooth
enamel overlay= acellular, highly calcified -hard!
root of tooth
dentin with cementum overlay
what is to note about dentin, enamel and cementum
similar to bone, but avascular
neck of tooth
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 is made up of
only muscularis externa (skeletal muscle) and mucosa (stratified squamous epithelium)
Esophagus
where is it located?
pass through?
exceptions?
posterior to trachea
passes through diaphragm to the abdominal cavity
all 4 histological layers in GI tract from this point on
exceptions:
muscularis externa
-upper 1/3 -skeletal muscle
-middle 1/3 -skeletal and smooth muscle (transition zone)
-lower 1/3 -smooth muscle
has adventitia in mediastinum (outermost layer) =fibrous CT (no epithelium)
Stomach
what are the 4 regions?
cardiac region (cardia) -attached to esophagus
fundus -above esophageal entrance
body
pyloric region (pylorus) -has pyloric sphincter
greater and lesser curvatures
converts food into chime (food +gastric juice)
stomach mucosa, invaginations of epithelium form…
invaginations of epithelium form gastric glands (exocrine) -secrete gastric juice to lumen
gastric glands of mucosa contain in stomach
chief cells
parietal cells
goblet cells
G cells (enteroendocrine cells)
chief cells from gastric gland
secrete pepsinogen + gastric lipase enzymes
parietal cells from gastric gland
secrete HCl + intrinsic factor (for vit B12 absorbance in ileum)
Goblet cells from gastric gland
-mucus (surface epithelium also contains many goblet cells along with the gastric glands)
G cells (enteroendocrine cells) of gastric gland
secrete gastrin (hormone to blood)
rugae of stomach
folds of mucosa + submucosa due to contraction of muscularis mucosa
allows for expansion without tearing mucosa
muscularis externa of stomach
3 layers
function= churning
inner oblique
middle circular
outer longitudinal
Small intestine
3 segments
end of pyloric sphincter to ileocaecal valve
duodenum
jejunum
ileum
duodenum of small intestine
first fold (short) -retroperitoneal extra glands here secrete alkaline mucus to protect against stomach acid
jejunum of small intestine
middle section
ileum of small intestine
attached to caecum (part of large intestine)
has groups of lymph nodules =Peyer’s patches
prevent infection of small intestine and bacteria from entering blood
segments specialized to increase absorption SA of small intestine
plicae circulares -submucosa thrown into folds
villi -projections of mucosa into lumen
-contains blood capillaries and lacteals (lymph capillaries that absorb e.g. fats)
microvilli -brush border on enterocytes (simple columnar) -extend into lumen
within epithelium of small intestine separate enteroendocrine cells secrete the hormones
secretin
cholecystokinin
small intestine accessory organs
pancreas
liver
gallbladder
pancreas
retroperitoneal
parts: head, body and tail
contains exocrine portion and endocrine portion
exocrine portion of pancreas
acinar cells/ acini (most of pancreas)
-secrete digestive enzymes (into ducts)
duct cells -secrete alkaline fluids to neutralize stomach acid
pancreatic juice
digestive enzymes + alkaline fluid
endocrine portion of pancreas
islets of Langerhans (amid acini)
secrete hormones; insulin and glucagon to regulate blood
Liver
4 lobes right, left, caudate, quadrate
cells: hepatocytes
filters material from GI tract (nutrients, toxins) before going to rest of body
produces bile -for fat digestion
Gallbladder
muscular sac on surface of liver
rugae, no submucosa
stores, concentrates bile between meals
enzymes, alkaline fluid and bile enter duodenum via series of ducts
pancreas: accessory Pancreatic Duct to duodenum(in many people) and Pancreatic Duct to Hepato-Pancreatic Ampcilla to duodenum
liver to hepatic duct and gallbladder to cystic duct both connect to common bile duct which connects to hepato-pancreatic ampcilla to duodenum
Large Intestine
ileocaecal valve to anus
no villi or folds
consists of caecum, appendix, colon, rectum and anus
parts of colon
ascending (right side) hepatic flexure transverse splenic flexure descending (left side) sigmoid
Colon: muscularis externa longitudinal layer incomplete
=taeniae coli
contraction forms pouches =haustra
colon: epiploic appendages
=fat-filled pouches function unknown
rectum of large intestine
no taeniae coli
anal canal = last 3cm
anus
2 anal sphincters: internal (smooth muscle) + external (skeletal muscle -voluntary control)
Immune function for digestive system
lymph nodules in mucosa throughout small + large intestine
Peyers patches in ileum -prevent infection of small intestine and prevent bacteria from entering blood
Digestive function of lymph system
flow of vessels
most absorbed fats from small intestine enter lacteals (some into blood)
lacteals -> lymph collecting vessels -> cisterna chyli -> thoracic duct -> left subclavian vein
Lower GI tract blood circulation (vessel route)
Aorta -> superior or inferior mesenteric artery
superior mesenteric artery -> capillaries in small and large instestines -> superior mesenteric veins -> hepatic portal system
inferior mesenteric veins -> capilaries in small intestine -> inferior mesenteric vein -> splenic vein -> hepatic portal system
hepatic portal system -> capillaries in liver -> hepatic vein -> inferior vena cava
what makes up the hepatic portal system
capillaries in small and large intestine to capillaries in liver
blood does not flow to heart in between
peritoneum –serous membrane
- visceral peritoneum (against organ wall)
- -parietal peritoneum (against abdominal cavity wall)
- parietal cavity = filled with serous fluid
serosa between organs =
sheet of 2 fused visceral peritoneum layers
contains blood/lymph vessels and nerves
forms folds in some areas =omenta
greater omentum
“fatty apron”
covers transverse colon and small intestine
contains fat -protection, insulation, energy reserve
lesser omentum
suspends stomach from liver
mesentery
suspends small intestine from cavity wall
double layer of parietal peritoneum
retroperitoneal
an organ behind the peritoneum
peritoneum lines only one side
anterior= parietal peritoneum
posterior = CT (adventitia)
peritonitis
inflammation of the peritoneum
due to: burst appendix or wounds
