DIGESTIVE SYSTEM Flashcards
what is the function of the digestive system?
to break down the food we eat, release their nutrients, and absorb those nutrients in the body.
what is the workhorse of the digestive system?
the small intestine is where majority of digestion occurs.
the organs of the digestive system are divided into 2 main categories. what are they?
- alimentary canal
- accessory digestive organs
what is the alimentary canal and the organs it contains?
the alimentary canal is also called the gastrointestinal tract.
- the tube is about 25 feet long in length and starts at the mouth and ends at the anus.
- organs: mouth, pharynx, esophagus, stomach, small and large intestine, rectum, and anus.
MAIN FUNCTION: nourish the body.
what are the 4 tissue layers in the alimentary canal?
mucosa, submucosa, muscularis, and serosa
what is the “accessory digestive organs”?
each of the accessory digestive organs helps in the breakdown of food.
- within the mouth, the teeth and tongue begin mechanical digestion but the SALIVARY GLANDS begin chemical digestion.
- once food enters the small intestine, the GALLBLADDER, LIVER, PANCREAS release bile and enzymes for digestion to continue.
what is the mucosa?
first tissue layer.
- epithelium: in the mouth, pharynx, esophagus, and anal canal, the epithelium is stratified squamous epithelium. in the stomach and intestines it is simple columnar epithelium.
AMONG THE THE EPITHELIAL CELLS ARE GOBLET CELLS THAT SECRETE MUCUS INTO LUMEN AND ENTEROENDOCRINE CELLS THAT SECRETE HORMONES.
- lamina propria: connective tissue and has lymphatic and blood vessels
- muscularis mucosa: smooth muscle
what is the submucosa?
second tissue layer.
- includes blood and lymphatic vessels including the submucosal plexus/plexus of meissner: plays a role in regulation of secretion, blood flow, smooth muscle activity, etc.
what is the muscularis?
third tissue layer.
- double layer of smooth muscle: inner circular layer and outer longitudinal layer.
- responsible for the movement of the digestive tract through peristalsis
the mouth, pharynx, and proximal part of the esophagus, and anal sphincter, the muscularis is made up of skeletal muscle for voluntary control over swallowing and defecation.
what is the serosa?
fourth tissue layer.
- present only in the region of the alimentary canal within the abdominal cavity.
- instead of the serosa, the mouth, pharynx, and esophafus have adventitia.
what do the cranial nerves do for us when we eat?
- able to feel the food so we dont bite ourselves
- provide taste to the food
what is the function of blood vessels in terms of the digestive system?
- transport protein and carbohydrate nutrients after the food is digested.
- supply organs of the alimentary canal with nutrients and oxygen needed to drive their cellular processes.
what arteries supply the alimentary canal, liver, stomach, duodenum. small intestine, large intestine?
- proximal parts of the alimentary canal supplied with arteries branching off of the aortic arch and thoracic aorta.
- inferior part of the alimentary canal: arteries branching off of the abdominal aorta.
- liver, stomach, duodenum: celiac trunk
- small and large intestine: superior and inferior mesenteric arteries
the veins that collect the nutrient rich blood from the small intestine empty into the?
hepatic portal system which takes the blood to the liver where the nutrients are either processed or stored for later use. then the blood goes back to the heart.
the digestive organs within the abdominal cavity are held in place by the?
peritoneum. made up of parietal peritoneum which lines the abdominal wall, visceral peritoneum which surrounds the organs, and in between is the peritoneal cavity including the fluid.
the processes of digestion include 6 activities:
ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation
what is ingestion?
ingestion refers to the entry of food into the alimentary canal through the mouth.
- the food is chewed and mixed with saliva that contain enzymes that break down carbohydrates and some lipids.
what is propulsion?
movement of food through the digestive tract.
- peristalsis is the contraction and relaxation of the longitudinal and circular muscle layers of the wall in the alimentary canal which propel food along.
what is mechanical digestion?
purely physical process that does not change the chemical nature of the food.
- involves chewing/mastication and tongue movements to make food into smaller pieces.
- occurs in the mouth, the stomach does mechanical churning of food and when mixed with gastric juices becomes chyme, and also in the small intestine via segmentation
what is chemical digestion?
chemical digestion is the breakdown of complex food molecules into their building blocks. ex: protein into amino acids.
- chemical digestion begins in the mouth, then stomach, and then small intestine which is the primary site and it is completed here.
what is absorption?
absorption is the process by which nutrients from digested food enter the bloodstream or lymphatic system.
- small intestine is the primary site of absorption.
- large intestine: absorption here primarily involves reabsorption of water and electrolytes, and maybe some vitamins.
what is defecation?
the final step in digestion, undigested materials are removed from the body as feces.
what is the oral cavity?
cheeks, tongue, and palate.
the lips/labia regulate what comes in and out of the mouth and responsible for facial expressions.
the main open area of the mouth/oral cavity runs from the?
gums/teeth to the fauces.
talk about the palates: hard and soft?
roof of the mouth:
the hard palate is bony: palatine and maxilla.
the soft palate is muscular: allows for swallowing, singing, yawning.
what is the uvula?
small tissue hanging down from the soft palate that helps prevent food from entering the nasal cavity during swallowing.
what is the tongue attached to?
mandible and styloid processes of temporal bones and the hyoid bone.
- intrinsic and extrinsic muscles that are responsible for optimal chewing, gather food into bolus, position food so it can be swallowed.
papillae: extensions of lamina propria of mucosa that contain taste buds and touch receptors.
what are the major salivary glands and what does saliva contain?
saliva composition: 95% water, ions, enzymes, glycoprotein
major types: submandibular, sublingual, parotid glands
what is the function of saliva?
lubricate food, facilitate movement, swallowing, bolus formation
what glands secrete salivary amylase and what does it do?
the parotid glands are major salivary glands that secrete salivary amylase which is an enzyme that begins the chemical digestion of starch. it breaks down starch into simpler sugars.
