Lecture Outline #24: Digestive System Flashcards
digestive system function #1
mechanical processing
- chewing (mastication) - gives more surface area for enzymes
- churning of stomach
- segmentation in small intestine
digestive system function #2
chemical breakdown
- sugars, lipids, proteins
digestive system function #3
secretion of acids/enzymes/buffers
- by GI tract
- by accessory organs: pancreas, liver
digestive system function #4
absorption across gut epithelium into BVs
- mainly occurring in SI
- nutrients, electrolytes, vitamins, water
- water absorption mainly occurs in small mesenteric vein to the liver
digestive system #5
dehydration, compaction, excretion
- dehydration and compaction mainly happens in large intestine
- defection of feces
gut - what is, what are the parts
gut - alimentary canal/GI tract, as a whole it is a muscular tube extending from mouth to anus
Make up of diverticula
1. Foregut - mouth, esophagus, stomach, duodenum
2. Midgut - (main absorption) jejunum, ileum
3. Hindgut - colon, rectum, part of anus
accessory organs of gut
tongue, teeth, gastric & intestinal glands
foregut accessory organs - liver, gallbladder, pancreas, salivary glands
the oral cavity
tongue, teeth, lips, cheeks, hard/soft palates
- place of mastication and bolus formation
lips & cheeks
cheeks - buccinator m.
lined with mucous membrane
orbicularis oris - CN VII: keep food in mouth
labial frenulum (superior & inferior lines on centers of gum) stabilized lips
vestibule - space btw lips/cheeks and teeth/gums
uvula
part of soft palate - ball dangly thingy
gingiva
gums
mucosa epithelium covering alveolar bone/hard palate
parotid glands
innervated by IX
anterior to ear
drained by stenson’s duct
submandibular glands
innervated by VII
beneath tongue and sublingual gland
drained by Wharton’s ducts
sublingual glands
innervated by VII
beneath teeth
drained by bartholin’s ducts
saliva
cleans teeth and moistens food
has amylase enzyme to break down starch
protects enamel when acid reflux occurs
tongue
intrinsic m.s run in every direction, XII
muscular hydrostat - m. maintains volume but changes shape
anchored to hyoid & mandible
stabilized by lingual frenulum (attaches tongue to mandible)
ankyloglossia
tongue too tightly bound to floor of mouth by lingual frenulum
hairy tongue (lingua villosa)
hypertrophy of filiform papillae from poor oral hygiene
soft palate
muscular flap, continuation of hard palate
divides naso-/oropharynx during swallowing
hard palate
palatine & maxillary bones
teeth
3 parts
1. crown
2. neck
3. root
innervated by inferior and superior alveolar n.s
attach to V2 and V3
three materials of teeth
- Enamel (crown): calcium phosphate - hardest substance
- Dentin (body of teeth): not as hard, forms, root & encloses the pulp cavity
- cementum: cements each into the socket
pulp cavity
contains NAVLs
root canal: narrow tunnel thru each root
gomphosis
fibrous joint that anchors the root of tooth into the bony alveolar socket
incisors
8 of them
1 root
blade-shaped cusp
for chisling
cuspids
4 of them
1 root
conical-pointing cusp
for holding onto things
bicuspid
8
2 premolars
1-2 roots
blade-like cusps
molars
8-12 of them
3-4 roots
large-flattened crowns
for grinding
deciduous teeth
around 20 teeth that erupt between 6 mo to 2 yrs
non-deciduous teeth
around 28-32 teeth that erupt around 6-21 yrs
alveolar process
surrounds tooth root, lose tooth=loose process
braces
align and straighten teeth
impacted molars
grow sideways into another tooth
on lower jaw = not bad
on upper jaw = roots of teeth are in maxillary sinus so when you take out teeth, there is a connection of sinus and oral cavity for air to flow
root canal dental implants
procedure where drill is pushed through enamel all the way to the root and take the pulp out. The tooth is filled with a hard compound
mandibular tori
bony growth on medial side of mandible
gut layers - mucosa
innermost tunic for surface area and protection
made of mucous membrane
ANS controls mucous secretions that protect gut lining
rugae (plicae circularis) for pleated appearance/more SA
epithelium is supported by lamina propria (CT)
villi (columnar epithelium/Goblet cells) for SA for more nutrient exchange
gut layers - submucosa
contains exocrine glands for enzyme secretion
is highly vascular (NAVLS) for absorption of nutrients
has ANS fibers called meissner’s plexus to control exocrine secretions
gut layers - muscularis
2 muscle layers for peristalsis = muscular directional contractions, the further the stretch of m.s the harder the contraction
inner layer - circularis m.s to pinch food, decreases diameter and increases length
outer layer - longitudinal m.s to shorten food, decrease tube length and increase diameter
myenteric plexus (of ANS fiber) controls peristalsis/segmentation (mixing) of chyme
gut layers - serosa
outermost layer
is a serous membrane (visceral peritoneum)
esophagus
collapsible muscular tube of inner & outer muscularis layers, submucosa & mucosa.
extends from pharynx to stomach through esophageal hiatus of diaphragm
bolus movement to esophagus
- foot enters oral cavity
- mastication - bolus formation
- bolus moves to back of mouth to swallow
- soft palate rises to close nasal cavity
- epiglottis lowers over trachea
- bolus is swallowed into esophagus
regions of stomach
- cardia - entrance to stomach with cardiac sphincter
- fundus - bulging domed aspect
- Body - with greater and lesser curvatures w/ respective omentums
- pylorus - end of stomach with strong pyloric sphincter
walls of stomach
3 layers of m.s (outer, inner, and oblique layers) to squish and churn food to lower pH level of 2
internal surface is covered in rugae
produces gastric juices (HCl, pepsin, rennin) to kill bacteria and mucous to protect walls from gastric juices
stores ethanol, water, and aspirin which goes directly into bloodstream
gastric ulcer
open sore in the stomach lining
gastric reflux/gastroesophageal reflux disease
chronic condition when stomach acids leak back into esophagus through cardiac sphincter
congenital diaphragmatic hernia
birth defect that occurs when diaphragm doesn’t form properly, leaving a hole that allows abdominal organs - mainly stomach - to move into chest cavity
paraoesophageal hernia
a large portion of the stomach or other bowel organs are pushed up into the chest
hiatal hernia in utera (pregnant women)
a portion of the stomach penetrates the hiatus of the diaphragm, esophagus and stomach slide up
small intestine
mucosa has plicae circularis and villi to increase SA as well as microvilli
Is 20 - 25 ft long with three parts (duodenum, jejunum, and ileum)
duodenum
8-12 inches long
place where pH neutralization occurs to bring pH level up to 7 (buffers do this)
mixing bowl of chyme
submucosal glands produce mucous & buffers
mucosa layer is thin
contains MALT & peyers patches
hepatopancreatic sphincter is below duodenal papilla
jejunum
7-9 feet long
dense mucosa
majority of digestion, some absorption
functions are done through enzymes secreted from pancreas through duodenum and combined with jejunum’s own enzymes
ileum
8-14 feet long
medium thickness mucosa
final digestion, majority absorption
contains GALT
ileocecal valve - controls flow of chyme into cecum
krohn’s disease
no plicae circularis, less absorption of nutrients
colon
where dehydration, absorption, and compaction of chyme occurs which becomes feces.
5 feet long, big lumen, and has less longitudinal & circularis m.s so feces is slow moving
haustra - pouches formed by colon musculature, where circular m.s meet
tenia coli - 3 longitudinal ribbons of muscle that come together at vermiform appendix
epiploic appendages - fat
colon sections in order
cecum
ascending colon (10-16”)
hepatic/right colic flexure - beneath liver
transverse/mid colon (10-16”)
splenic/left colic flexure - beneath spleen
descending colon (10-16”)
sigmoid flexure
sigmoid colon (8-16”)
vermiform appendix
vestigial remnant
blind pocket with little lymphoid function
diverticula
diverticulosis
diverticulitis
- out-pocketing of colon wall
- abnormal diverticula (small pouches/hernias) that form on colon walls
- inflammation of abnormal diverticula mainly in sigmoid colon, can pop once it swells enough and feces gets into peritoneum and abdominal cavity = sepsis
GI tract innervation
at splenic flexure, that last third of tract is innervated by pudendal nerve, everything above is vagus nerve
rectum
6-8” long
contains baroreceptors to monitor pressure
highly muscular termination of colon
when feces enter - urge to defecate
epithelium is keratinized - abrasion-resistant
anus
muscular valves at terminus of rectum = verge-pockets that hold feces
contain baroreceptors
internal anal sphincter - ANS involuntary smooth m.
external anal sphincter - voluntary skeletal m.
can get internal & external hemorrhoids
food flow
(food) through orbicularis oris (bolus) - oral cavity - oropharynx - esophagus - through cardiac sphincter (chyme) - stomach - through pyloric sphincter - duodenum - jejunum - ileum - through ileocecal valve (feces) - cecum - ascending colon - transverse colon - descending colon - sigmoid colon - rectum - through external anal sphincter - through internal anal sphincter - anus
ileostomy
resection of portion of gut
defecate through small intestine stoma, whole LI is taken out
colostomy
resection of a portion of gut
stoma in abdominal wall for defection
rectum & anus is taken out
accessory structure - liver
largest organ in body
large blood reservoir
has R/L lobes, caudate & quadrate (gallbladder) lobes
metabolizes carbohydrates, lipids, amino acids
stores vitamins and minerals
detoxify/remove waste products (ammonia/urea)
inactivate/remove various drugs & hormones
produce bile to emulsify lipids
liver - vasculature
common hepatic artery from celiac trunk of aorta to become hepatic proper artery
arteries through capillary beds in GI = hepatic portal v.s
hepatic veins return blood to IVC
gallbladder
hollow, thin muscular sac for storing excess bile
has a fundus (ending), body, and neck
bile
makes feces brown
produced by liver to emulsify lipids = not digest but take apart food to increase SA, lipase breaks down
hepatopancreatic sphincter
regulatory m.
if constricted (no food) = bile backs up into common bile duct to cystic duct (2-way) and into gallbladder for storage
if dilated (food) = gallbladder contracts and inject bile into duodenum
cholecystitis
inflammation of gallbladder
cholelithiasis
presence of gallstones in gallbladder
stones are normally cholesterol based and can get stuck in cystic duct
cirrhosis (hepatitis)
destruction of hepatocytes due to:
1. exposure to drugs (ethanol replaces hepatic tissue with scar tissue = decrease function)
2. viral infection (hep C)
3. blockage of hepatic ducts
hepatic portal hypertension
if blood cannot drain via HPV, finds alternate routes
- thrombosis, cirrhosis, fibrosis found in liver
- back from through several portocaval anastomes
- metabolizes escape
pancreas
elongate organ with lumpy, granular texture
located btw stomach & duodenum
highly vascular - drains to HPV
endocrine f(x)s - 1%
exocrine f(x)s - 99%
endocrine functions
uses blood
secretions
- through hepatic portal system
1. glucagon - raises glucose levels in blood
2. insulin - lowers blood glucose levels
can get diabetes II if eating an overabundance of starches and sugars
exocrine functions
uses ducts
secretions - enzymes
- through pancreatic duct into duodenum
1. proteinases - degrade proteins
2. lipases - degrade fats
3. nucleases - degrade DNA & RNA
lactose intolerant
not enough lactase enzymes
food ferments in GI
hydrogen & methane produced = bloated
serous membranes
abrasion resistant
1. parietal peritoneum lines peritoneal cavity
2. visceral peritoneum covers organs
mesenteries
BVs go through these to organs, supports/protects NAVLs
durable, double layer of serous membrane
suspends GI tract from walls of cavity
peritoneal cavity
full of serous fluids
GI tract is not in it but goes through it
intraperitoneal organs
pass through peritoneal cavity
organ is free moving
suspended by a mesentery
jejunum & ileum
secondarily retroperitoneal organs
initially free-moving, suspended by a mesentary in the cavity, now moved behind peritoneum
organ is stationary
only laminated on one side
duodenum
pancreas
asc & desc colon
retroperitoneal organs
outside peritoneal cavity
easy surgical access
organ is stationary
urogenital system
abdominal aorta
IVC
kidneys
mesentery proper
encloses the jejunum & ileum
mesocolon
suspends transverse & sigmoid colons
lesser omentum
btw stomach & liver with common bile duct running within
greater omentum (mesogaster)
extends from greater curvature
site of fat storage & fights infections
stomach to transverse colon
creates a double layer over small intestine
coronary ligament
suspends liver from diaphragm
falciform ligaments
btw liver & abdominal wall @ umbilicus
contains ligamentum venosum
round ligament
ventral mesentary
