22-1: Digestive Processes and Histology Flashcards
What are the functions of the digestive system?
to take in food, break it down into tiny nutrient molecules, absorb these molecules into the bloodstream, and rid the body of indigestible remains
What are the two sets of organs in the digestive system?
the GI tract (where food passes thru) and the accessory organs (food doesn’t pass thru them)
GI Tract
long muscular tube winding thru the body, which digests food (breaks it down into small fragments) and absorbs the digested pieces through its lining into the blood. Includes:
mouth pharynx esophagus stomach small intestine large intestine anus
accessory organs
produce or store secretions that aid in the breakdown of food, and release them into the GI tract through duct, making them exocrine glands. Includes:
salivary glands
liver
gall bladder
pancreas
What are the 6 digestive processes?
ingestion propulsion mechanical digestion chemical digestion absorption defecation
ingestion
process of taking food into the GI tract (occurs int he mouth)
propulsion
the process that moves food through the GI tract. Includes swallowing (oropharynx) and peristalsis (esophagus to intestines)
peristalsis
wavelike contractions of the smooth muscle in the walls of the GI tract that squeeze food from one organ to the next
(“peristalsis pushes” - linear motion of outer layers)
segmentation
rhythmic local constrictions
“segmentation squishes” - circular motions of inner layers
mechanical digestion
physically breaking down the food into smaller pieces, including chewing, mixing of food with saliva by tongue, churning of food in stomach, and segmentation in intestines
chemical digestion
series of catabolic steps in which complex food molecules are broken down into their monomers with the help of enzymes
absorption
the passage of digested end products from the lumen of the GI tract into the blood or lymph. The major site for this process is the small intestine
defecation
the elimination of indigestible substances from the body via the anus in the form of feces
What are the four tissue layers of the GI tract, from deep to superficial?
mucosa
submucosa
muscularis
serosa
mucosa
moist layer of epithelial tissue lining the lumen of the tube from mouth to anus
what are the functions of the mucosa?
- secretion of mucus and digestive enzymes
- absorption of the end products of digestion into the blood
- protection against infection (from lymph nodes - MALT)
lamina propria
capillaries for absorption, lies under the epithelial tissue in the mucosa
submucosa
layer of dense connective tissue that binds the mucosa to the muscularis. Highly vascular and contains elastic fibers that enable the stomach to regain its normal shape after stretching
muscularis
two layers of smooth muscle (inner circular and outer longitudenal) - contractions of this layer mix food with digestive juices (segmentation) and propel it through the GI tract (peristalsis).
sphincters
circular layer of musclaris thickens to act as valves to prevent back flow and control food passage from one organ to the next
serosa
protective outermost layer covering organs in abdomen. formed of connective tissue covered by a single layer of squamos epithelial cells
visceral peritoneam
aka serosa, covers organs in abdomen
parietal peritoneum
lines walls of abdominal cavity
peritoneal cavity
space between the parietal and visceral peritoneam, filled with serous fluid
peritonitis
inflammation of the peritoneal cavity
