Chapter 23 The Digestive System Flashcards
Function of digestive system
- Food intake
- Digestion of food into nutrient molecules
- Absorption of nutrient into blood
- Elimination of waste
Alimentary Canal + Accessory Organs
Mouth, tongue, salivary glands (parotid gland, sublingual gland, submandibular gland), pharynx, stomach, pancreas, liver, gallbladder, duodenum, jejunum, ileum, large intestine stuff….
Divisions of Digestive system
- Alimentary canal- gastrointestinal tract, from mouth to anus, contents outside of body
- Accessory digestive organs- physical breakdown and propulsion of foodstuffs: teeth and tongue; chemical breakdown of foodstuffs: gallbladder, salivary glands, liver, pancreas
Abdominal quadrants
4 quadrants R/L Upper/Lower
Abdominal Regions
Right Hypochondriac| Epigastric | Left Hypochond
Right Lumbar | Umbilical | Left Lumbar
Right iliac (inguinal) | Hypogastric| Left iliac (inguin)
4 layers of alimentary canal wall
External to internal:
serosa, muscularis externa, submucosa, mucosa
Mucosa
Innermost layer- lines lumen
3 layers:
- epithelium - continuous with ducts that dump into lumen
- Lamina propria (CT)- vasculature for absorption
- Muscularis mucosae (smooth muscle)- local movement of mucosa
Submucosa
- CT- rich in elastic fibers
- blood vessels, lymphatic vessels, nerves
Muscularis Externa
- 2 layers of smooth muscle: circular layer, longitudinal layer (sometimes circular layer thickens in areas to become sphincter)
Serosa
- visceral peritoneum
- simple squamous epithelium (mesothelium)
Smooth muscle tissue
6 major locations:
- iris of eye
- walls of blood vessels
- respiratory tubes
- digestive tubes (muscularis mucosae, muscularis externa)
- urinary organs
- reproductive organs
Smooth muscle anatomy
Irregularly arranged thick and thin filaments thus no striations
- intermediate filaments of the cytoskeleton attach to dense bodies (similar to z-discs)
- contraction occurs in a corkscrew fashion, pulling dense bodies closer together
Peritoneum
serous membrane of the abdominopelvic cavity
Mesentery
double layer of peritonem
- holds organs in place
- stores adipose
- route for vessels to/from the organs
Dorsal mesentery
extends dorsally from the alimentary canal to the posterior abdominal wall
- Greater omentum - greater curvature of stomach, around transverse colon to posterior wall of abdomen
- contains fat
- mesentery- long coils of jejunum and ileum supported
- transverse mesocolon- holds transverse colon to posterior abdominal wall (almost horizontal)
- sigmoid mesocolon- connects sigmoid colon to posterior pelvic wall
Ventral mesentery
extends ventrally from the stomach and liver to anterior abdominal wall
- falciform ligament - binds anterior aspect of liver to anterior abdominal wall/diaphragm
- lesser omentum runs from the liver to the lesser curvature of the stomach and beginning of duodenum
Retroperitoneal organs of GI tract
lack peritoneum…fuse to the dorsal abdominal wall
- duodenum, ascending colon, descending colon, rectum, pancreas
Intraperitoneal Organs and their mesenteries
Liver (falciform, lesser omentum) Stomach (greater and lesser omentum) ileum/jejunum (mesentery) transverse colon (transverse mesocolon) sigmoid colon (sigmoid mesocolon)
Mouth and associated organs
oral cavity
- mucosa-lined cavity
- very thick stratified squamous epithelium
Tongue
- Internal muscles change shape of the tongue; not attached to any bones
- External muscles change the position of the tongue; attached to bones of the skull and hyoid
Surface anatomy of the tongue
posterior 1/3- lingual tonsil- oropharynx, sulcus terminalis
Anterior 2/3- circumvallate papillae, fungiform papillae (reddish), filiform papillae (most abundant, roughened, white appearance)
Salivary glands
Parotid- big, backwards
Sublingual- under tongue
Submandibular- below mandible, back (duct more anterior than sublingual ducts)
Saliva cleanses teeth and dissolves food; body makes 2-4 pints a day?
Pharynx is part of both_______ systems.
Respiratory/digestive
Esophagus
- collapsible muscular tube
- laryngopharynx -> stomach
Muscularis externa:
top 1/3 -skeletal muscle
mid 1/3- skeletal and smooth
end 1/3- smooth muscle
Microscopic anatomy of esophagus
Mucosa (stratified squamous epithelium), submucosa, then muscularis externa ( 2 layers circular, longitudinal)
Stomach
- widest part of ealimentary canal
- food temporarily stored (4 hours) and made into chyme
- first site of chemical breakdown (pepsin)
Gross anatomy of stomach
Hard to explain, know it…
Chief cell secretes?
pepsinogen
Parietal cell secretes?
HCl
Small intestine
longest part of alimentary canal
- site of most enzymatic digestion and almost all absorption of nutrients
- segmentation- moves chyme all around increasing contact with absorptive mucosal lining
- peristalsis- propels chyme through SI
Gross anatomy of SI
duodenum- c shaped (12 finger widths long)
Jejunum- Upper, 40% of small intestine
Ileum- (longest part) Lower, 60% of small intestine
Pilcae circularis?
permanent, transverse circular folds of the mucosa and submucosa which aid in segmentation and increase surface area for absorption: 1 tall
Villi?
Finger-like projections in the mucosa which are ~1mm tall and viewable with eye
- Enterocytes/absorptive cells- simple columnar epithelium specialized for absorbing digested nutrients
Microvilli?
Tiny, finger-like projections on apical side of each simple columnar epithelial enterocytes of the villi
Large intestine
- receives undigested food from small intestine
- absorbs water and electrolytes
- pass feces out of gi tract
- mass peristaltic movements vs. constant peristalsis
Teniae Coli?
3-longitudinal strips running the length of the LI
- thickenings of the longitudinal layer of the muscularis externa
Haustra?
sac-like bulges formed by the muscle tone of the large intestine
Epiploic appendages?
fat- filled pouches of visceral peritoneum that hang from the intestine
- unknown significance/function
Anal sphincter anatomy
Levator ani muscle, external anal sphincter, internal anal sphincter, anus
Defecation
Stretch of rectal wall due to feces-> cerebral cortex (conscious control)-> voluntary motor nerve to external anal sphincter-> inhibition of voluntary motor neurons allowing external anal sphincter to relax so feces may pass
Goblet cells of LI
need lots of goblet cells because of mass movements of solids?
More goblet cells found proximally near the ileum
Liver
- largest gland in the body
- bile production- green liquid (alkaline) stored in the gallbladder
Gallbladder
- muscular sac on the underside of right lobe of liver
- stores and concentrates bile
Know ducts that transport bile
- right/left hepatic duct, common hepatic duct (joins with cystic duct from gallbladder) to exit to the duodenum by the common bile duct
Pancreas
- exocrine function= enzymes for digestion in small intestine
- endocrine function = hormones for glucose regulation
