Digestive System Composition and Processes

the gastrointestinal tract, the 3 pairs of salivary glands, the liver, the gallbladder, and the pancreas

ingestion, mechanical digestion and movement, secretion, chemical digestion, absorption, and elimination

taking in food through the oral cavity

chewing breaks food into smaller pieces, and two types of movement, segmentation and peristalsis, mix it and propel it forward

peristaltic movement is a ring of contraction along the wall of the tube, allowing food to be pushed forward due to the area beyond the wall relaxing

contraction and relaxation occur randomly, which moves contents within the lumen. food particles are pressed against the mucosa, which helps absorb nutrients

the secretion of fluid, digestive enzymes, acid, alkali, bile, and mucus into the GI tract at various locations. several hormones that regulate digestion are also secreted into the bloodstream

contents in the lumen are broken down into smaller nutrient molecules using specific enzymes like starch amylase

nutrient molecules passing through the mucosal layer of the GI tract into the blood or lymph

the expulsion of undigested material in the body

the mucosa, the submucosa, the muscularis, and the serosa

the innermost layer of squamous epithelium cells, mostly simple columnar. it is the site of secretion and absorption

dense CT with blood and lymph vessels, lymph nodules, and nerves

2-3 layers of smooth muscle. contains sphincters (specialized circular smooth muscle) that regulate movement through the GI tract

outermost serous layer composed of visceral peritoneum. it protects underlying tissues and secretes serous fluid for lubrication

the stomach and both intestines are lined with simple columnar epithelium. the oral cavity is stratified squamous, keratinized for the lips and nonkeratinized for the other parts (like the esophagus' mucosa layer)

the ANS maintains muscle tone and regulates the strength, rate, and velocity of muscle contractions and regulations secretions

it decreases the rate of muscle contraction and secretion (SMOOTH muscle)

it increases the rate of muscle contraction and secretion (SMOOTH muscle)

they are arranged into nerve plexuses called the submucosal plexus (controls secretions) and myenteric plexus (controls motility)

the entrance to the GI tract lined by stratified squamous epithelium because it is subject to abrasion

it receives food and begins mechanical digestion via mastication and moving them with saliva to form a bolus for swallowing. it forms speech and receives tastes

they form a ring of lymphoid tissue including the pharyngeal, lingual, and palatine (paired) tonsils

they protect the entryway to the body from harmful microbes

there are 20 primary teeth and 32 permanent teeth. they consists of a crown (visible region) and root (below gingiva). enamel covers the crown, dentin is below the enamel, and pulp is below the dentin

teeth are for mastication (tear, grind, and break food into smaller pieces). they are innervated by the trigeminal nerve (CNV). a bundle of vessels pass through the root canal

the death of a tooth nerve caused by blocked blood flow

a thick, muscular organ lined by a mucous membrane, anchored to the hyoid bone and the frenulum

it mixes food particles with saliva during chewing, moves/positions food below the teeth for chewing, and moves food toward pharynx during swallowing

the passageway from the oral cavity to the esophagus/larynx

behind the nasal conchae, contains the pharyngeal tonsil and eustachian opening

below the nasopharynx and behind the uvula, contains the palatine and lingual tonsils

common entryway from trachea to the esophagus (notice the epiglottis)

when food enters the pharynx, the swallowing reflex is triggered. once it is triggered, it CANNOT be stopped

a collapsed, hollow, muscular tube lying behind the trachea. it is about 12 inches in length, and lined by stratified squamous epithelium. it penetrates through the esophageal hiatus to the diaphragm to enter the abdominal cavity

carries solid foods/liquids to the stomach

it is a collapsed region at the terminal end of the esophagus that prevents acidic stomach contents from backing up into the esophagus. fun fact: this is what causes heartburn

there is an abrupt epithelial change from stratified squamous epithelium to simple columnar epithelium with goblet cells (form gastric glands). this means the area is subject to dysplasias or pre-cancerous conditions due to cells losing control of mitosis

it stores food, chemically digests proteins, absorbs lipid-soluble substances, and regulates delivery into the small intestine. it empties in about 2-6 hours

they secrete gastric juice (2-3 L/day, pH 1.6-2.6). the epithelium of the stomach has millions of gastric pits that lead to gastric glands

one type of gastric gland cell. it produces mucous to protect the stomach mucosa

another gastric gland cell. secretes pepsinogen, an inactive form of the pepsin enzyme

final gastric gland cell. secretes pre-hydrochloric acid which becomes HCl and intrinsic factor

the parasympathetic nervous system regulates the release of gastric juice

an empty stomach has tonic muscle contraction to keep it small. after eating, tonic contractions cease and the stomach relaxes and stretches to accommodate the food, which allows for volume increase. 2-6 hours later, the stomach contractions so secretions move to the small intestine. mixing waves mix the stomach contents with stomach secretions to form chyme, and gastrin and the stretch of the stomach stimulate emptying

it begins right after the pyloric sphincter and extends to the ilio-cecal junction (about 20 ft). contains circular folds, villi (mucosa projections) and microvilli (simple columnar epithelial cells)
duodenum: first division, 10 inches. receives bile via the common bile duct from the liver and gallbladder, receives pancreatic juice via the pancreatic duct from the pancreas, and the sphincter of Oddi controls emptying these ducts
jejunum: the left side of the small intestine
ileum: right side of the small intestine, joins the large intestine at the ilio-cecal joint

absorbs about 90% of absorbable nutrients

releases 1-2 L/day, pH of 7.4-7.8. it includes mucous (alkaline) which neutralizes stomach acids that protect against stomach acids and digestive enzymes. also contains digestive enzymes for proteins, carbs, lipids, and nucleic acids and hormones that control pancreaticallbladder secretions

the distension of the intestinal wall stimulates parasympathetic reflexes that cause secretions

the stretch of smooth muscles, local reflexes, and the PNS stimulate contractions of the GI wall

begins at the cecum and ends at the anus (5ft). the laminal surface is lined with simple columnar epithelium up to the anal canal, then becomes the stratified squamous epithelium

it absorbs water, electrolytes, and vitamins, performs last stages of chemical digestion through normal flora actions, and compacts intestinal contents into feces and eliminates semisolid waste

the cecum, the colons, the rectum, the anal canal, and the anus

first portion of the large intestine; blind-ended pouches with vermiform appendix (lymphoid tissue)

ascending colon (up to right colic flexure), transverse colon (right to left colic flexure), descending colon, and the sigmoid colon

the straight portion that connects colon to anus, it contains a trio of transverse folds called rectal valves, which separate feces from gas to prevent simultaneous passage

begins when the rectum passes through the pelvic floor. puborectalis does all the work

mucous is secreted to protect the intestinal lining and HCO3- (bicarbonate) by epithelial cells. NA+ is absorbed by active transport and water is absorbed via osmosis

segmental movements mix the colon's contents, mass movements are big peristaltic contractions (3-4/day)

the elimination of feces (unabsorbed substances, bacteria, and old epithelial cells)

triggered by a deep breath and contracting abdominal wall muscles. this increases abdominal pressure, forcing feces into rectum. it triggers peristaltic waves and the internal anal sphincter relaxes. voluntary activation needs the puborectalis and external anal sphincter to RELAX

parotid: sides of cheeks before the ears
sublingual: below the tongue
submandibular: below the jaw at an angle

it moistures food and begins carb digestion. it is produced (1000-1500mL/day) continuously, most of it being water. a small amount is salivary amylase and mucin

an enzyme that begins starch digestion, located in the oral cavity

mucous protein that holds food particles together

inhibits bacterial growth

HCO3-, maintains pH 6.5-7.5 for enzymes

sympathetics stimulate small secretions of viscous saliva, parasympathetics stimulate large secretions of watery saliva

an elongated, pinkish-gray organ that is 6 inches in length extending from the duodenum to the spleen (BEHIND stomach)

endocrine: islets of Langerhans secrete hormones (ductless)
exocrine: acini secrete pancreatic juice by connecting to the duct system that forms the pancreatic duct (empties in duodenum)

1200-1500mL is produced each day. it is mainly water, but contains bicarbonate to neutralize gastric acids.

a large, vascular organ in URQ that is easily subject to trauma

it produces bile and manufactures plasma proteins (albumin and fibrinogen) from amino acids, and destroys RBCS and bacteria

neutralizes gastric acids and emulsifies fats/lipids which aid lipase action

it stores and concentrates bile (up to 10x as concentrated). cholycystokinin triggers the gallbladder to release bile, which is released as a response to the presence of lipids and proteins in the small intestine

partially digests starch, produced in pancreas and acts in small intestine

converts lipids to glycerol and free fatty acids. produced in the pancreas and released in the small intestine

makes the stomach very acidic, which kills bacteria and breaks down CT in meat, as well as activating pepsin

aids the absorption of vitamin B (metabolism) in the small intestine

the enterogastric reflex is triggered by distension of small intestine and inhibits peristalsis in the stomach to slow movement of food into the duodenum

smooth muscle

skeletal muscle

completes starch digestion, produced in small intestinal epithelium

digests proteins, produced in pancreas from trypsinogen, activated in small intestine

digests proteins, produced in stomach from pepsinogen, activated by low stomach pH

small polypeptides (amino acids)

glucose

nucleotides

emulsifies into smaller lipids which become monoglycerides and free fatty acids

lipids are emulsified, protected by the liver, concentrated by gallbladder, and released into the small intestine

breaks down nucleic acids