Digestive System Flashcards
What are the structures of the upper GI? (4)
- Mouth
- Pharynx
- Esophagus
- Stomach
What are the structures of the small intestine (part of the lower GI)? (3)
- Duodenum
- Jejunum
- Ileum
What are the structures of the large intestine (part of the lower GI)? (8)
- Cecum
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid
- Rectum
- Anal canal
- Anus
What are the accessory organs of the digestive system? (4)
- Salivary glands
- Liver
- Gallbladder
- Pancreas
What are the digestive processes? (6)
- Ingestion
- Secretion
- Motility (peristalsisis)
- Digestion
- Absorption
- Defecation
What is ingestion?
Taking food into mouth (aka eating)
What is secretion (in the digestive processes)?
Cells in the GI tract’s walls and accessory organs release H2O, acid, buffers, and enzymes into the tract’s lumen
What is motility (peristalsis)?
Alternating contraction and relaxation of the walls of the GI tract’s smooth muscles that moves food through in a wave-like manner
What is mechanical digestion?
Cutting/grinding food by teeth and GI tract movement aiding digestion
What is chemical digestion?
Series of catabolic reactions breaking down food macromolecules (carbs, lipids, nucleic acids, proteins) into usable smaller molecules
What is absorption (in the digestive processes)?
Passage of digestion’s end products from GI tract into blood/lymph for cell distribution
What is defecation?
Elimination of waste, indigestible substances, and bacteria/cells from GI tract
What are the phases of digestion? (3)
Cephalic, gastric, intestinal
What happens during the cephalic phase of digestion?
The vagus nerve (cranial nerve X) stimulates gastric secretion (from sensory/mental input) before food is even swallowed
What happens during the gastric phase of digestion?
Food stretches the stomach, activating myenteric/short and vagovagal/long reflexes
This causes the stomach to release hormones/acids (gastrin + histamine also stimulate)
What is the intestinal phase of digestion?
Inhibition of gastric stimulation and stimulation of chyme enters the duodenum
What are the layers of the GI tract? (4)
Mucosa (mucous membrane)
Submucosa
Muscular layer
Serosa
What makes up the mucosa layer of the GI tract? (4)
Epithelium
Loose connective tissue (lamina propria)
Some smooth muscle
Secretion Glands
What layer of the GI tract does absorption occur?
Mucosa
What makes the submucosa layer of the GI tract? (5)
Loose connective tissue
Glands
Nerves
Lymphatics
Blood vessels
What are the layers of smooth muscle of the GI tract’s muscular layer? (2)
Circular fibers: contract decreases diameter of lumen
Longitudinal fibers: contract shortens length of tube
What is the serosa layer of the GI tract?
Visceral peritoneum!
Protects underlying tissues
Secretes serous fluid which lubricates movement
What is the purpose of the gastrointestinal reflex pathways?
Regulates GI secretion and motility in response to stimuli in tract
What is the role of parasympathetic nerves (ANS) in the GI tract?
Causes increase in GI secretion and motility by increasing activity of enteric nervous system neurons
What is the role of sympathetic nerves (ANS) in the GI tract?
Causes a decrease in GI secretion and motility by inhibiting enteric nervous system neurons
What is the submucosal plexus (plexus of Meissner) of the enteric nervous system?
A network of neurons regulating movements of the mucosa, blood vessel vasoconstriction, and innervates secretory cells of mucosal glands
What is the myenteric plexus (plexus of Auerbach) of the enteric nervous system?
Has fibers from both divisions of the autonomic nervous system (ANS) and mostly controls GI tract motility
What is another name for the combination of saliva and chewed food in the digestive system?
Bolus
What is another name for the combination of digestive juices and bolus?
Chyme
Which part of the GI tract does the absorption of water?
Mainly the large intestine (lower GI)
Which accessory organ creates bile?
The liver
Which accessory organ stores bile?
Galbladder
What does the exocrine gland of the pancreas produce?
Enzymes (amylase, lipase, protease)
What does the endocrine gland of the pancreas produce?
Hormones (insulin, glucagon)
What is the gingivae?
The gums (covers tooth sockets and helps anchor teeth)
Hard vs soft palate of mouth
Hard palate (bony) forms most of roof
Soft palate (muscular) forms rest of roof
What is the function of the uvula (located in the mouth)?
Prevents swallowed food from entering nasal cavity
What is the oral vestibule?
Space between cheeks, lips, gums, and teeth
Frenulums of the mouth (3)
Superior labial frenulum attaches superior lip to gum
Lingual frenulum limits movement of the tongue posteriorly
Inferior labial frenulum attaches inferior lip to gum
What part of the mouth forms the floor, manipulates food for chewing/swallowing, shapes food, and senses taste?
Tongue
What is the fauces (located in the mouth)?
Opening between the oral cavity and oropharynx
What are the salivary glands? (3)
Parotid, submandibular, sublingual
What are the types of secretory cells of the salivary glands? (2)
- Serous: secretes water fluid with amylase (digestive enzyme)
- Mucous: secretes mucus which binds food particles and lubricates swallowing
What are the taste areas of the tongue? (4)
Bitter, sour, sweet, salty
What is the tongue composed of?
Skeletal muscle, mucous membrane
What is the tongue’s upper and lateral surfaces covered with?
Papillae (some have taste buds)
What structure of the mouth cuts, tears, and pulverizes food into smaller particles for swallowing?
Teeth
What is the function of the lingual glands?
Secretes lingual lipase
What structure of the mouth serves as receptors for gustation/taste and the presence of food in the mouth?
Taste buds
What is the function of the intrinsic tongue muscles?
They alter the shape of the tongue for swallowing and speech
What is the function of extrinsic tongue muscles?
Moves tongue from side to side and in and out for mastication, swallowing, and shaping into bolus
What is the cavity posterior to the mouth and connects to the esophagus?
Pharynx
What is the esophagus?
Straight collapsible tube pases behind the trachea through mediastinum and then through an opening in the diaphrahm (esophageal hiatus)
What is the upper espohageal sphincter made of?
Smooth muscle rings around upper esophagus
What is the lower esophageal (cardiac) sphincter made of?
Smooth muscle rings that allow food into the stomach when contracted (prevents reflux)
Do you breathe when swallowing food? (2)
No, when you swallow…
The uvula and palate seal off nasal cavity
Epiglottis covers larynx
What is gastroesophageal reflux disease?
Occurs when lower esophageal sphincter fails to close right after food enters stomach
(Contents of stomach reflux back to esophagus aka heartburn)
What structure is J-shaped enlargement of the GI tract that is pouch-like and has a capacity of 1 L?
The stomach
What are the folds of mucosa and submucosa in the stomach?
Rugae
What are the parts of the stomach? (4)
- Cardiac region (near esophagus)
- Fundus (temporary storage… balloons)
- Body (main part)
- Pyloris (forms canal and pyloric sphincter, connects to small intestine)
What are the functions of the stomach? (2)
- Mixes saliva, food, and gastric juices to make chyme
- Serves as food reservoir before release into small intestine
What are the small openings in the stomach’s mucus membrane?
Gastric pits
The gastric […] open into the gastric pits
Glands
What are the secretory cells of the stomach?
Mucous (goblet): secretes mucus (thin)
Chief cells: secrete enzymes
Parietal cells: secretes HCl (hydrochloric acid), intrinsic factors (helps B12 absorption)
What is the most important digestive enzyme secreted by the chief cells of the stomach?
Pepsin (secreted as pepsinogen then becomes pepsin when in contact with HCl)
What activates parasympathetic stimulation of the stomach?
Thinking/seeing/smelling/tasting food releases ACh (and gastrin) which stimulates gastric glands to make gastric juice
What do parietal cells of the stomach produce that are sent to the lumen?
Protons (H) that will combine with chlorid molecules from blood to make HCl
What slows gastric motility as food moves into the upper small intestine?
Cholecystokinin
What does the stomach absorb?
Small amounts of H2O, salts, alcohol, some drugs
What is the largest serous membrane of the body?
Peritoneum
What gland lies posterior to the stomach?
Pancreas
What does the pancreas produce that buffers stomach acid?
Sodium bicarbonate
Where does the pancreas empty its contents?
Duodenum
What does bile play a role in?
Emulsification of fats
What is the liver composed of? (3)
- Hepatocytes
- Bile canaliculi
- Hepatic sinusoids
Where does the majority of digestion and absorption occur?
The small intestine
What is the purpose of circular folds in the small intestine?
Increases surface area for digestion/absorption
What absorbs about 90% of nutrients and water that pass through the digestive system?
Small intestine
What is the function of segmentation in the small intestine?
Mixes chyme with digestive juices and brings food into contact with mucosa for absorption via contractions of circular folds
What is the function of peristalsis in the small intestine?
Propels chyme through small intestine via slow wave-like contractions of the longitudinal muscles (about 3-10 hours)
What are the finger-like projections of the mucosa covered with simple columnar epithelium?
Villi (rapidly reabsorbs fluid w/ digestive products)
Where are enzymes embedded in the mucosa of the intestines?
Epithelial cells of the intestinal mucosa
- Breaks down food just before absorption
Where are enzymes embedded in the mucosa of the intestines?
Epithelial cells of the intestinal mucosa
- Breaks down food just before absorption
What happens with too much peristalsis of the small intestine?
Diarrhea (peristaltic rush)
- Fluid and electrolytes cannot be absorbed normally
What is the cecum?
The start of the colon: dilated, pouch-like area that hangs slightly below ileocecal opening
What is the “turn” from the ascending colon to the transverse colon called?
Hepatic flexure
What is the largest and most moveable portion of the colon?
Transverse colon
What is the “turn” from the transverse colon to the descending colon called?
Splenic flexure (because it’s at the spleen)
What are the functions of the colon? (4)
- Bacteria converts proteins into amino acids, breaks down those acids, and produces some B vitamins
- Absorption of some water, ions, and vitamins
- Formation of feces
- Defecation
What are the haustra?
Small pouches caused by sac formation which gives the colon the segmented appearance
What is haustral churning?
Slow segmenting, uncoordinated movements of the haustra that occur every 25 min
- Walls squeeze contents onward
What are the colon’s ways of driving contents into the rectum? (3)
Haustral churning, peristalsis, mass peristalsis
What is mass peristalsis?
Strong peristaltic wave that begins in transverse colon and drives contents into rectum
What is the defecation reflex? (3)
- Receptors of rectal wall sense stretching and send impulses to the sacral spinal cord
- Motor impulses travel down descending colon, sigmoid colon, rectum, and anus
- Longitudinal rectal muscles contract and internal anal sphincter opens
What is Crohn’s disease?
Chronic inflammatory disease (all layers of bowel are inflamed)
What is peptic ulcer disease?
Mucosa erosion (stress, smoking, drugs, etc are risk factors)
What is hiatal hernia?
Opening where esophagus penetrates diaphragm (esophageal hiatus) is too big
What is Zenker’s diverticulum?
Pouch formed at pharyngoesophageal junction
What is volvulus?
Twisting of the bowel on itself (mostly newborns)
What is intussusception?
Telescoping of one portion of the bowel into the adjacent part (infants)
What is ulcerative colitis?
Chronic inflammation of the mucosa of rectum and colon
what is Diverticulosis?
Multiple Colon out pouches
what is Diverticulitis?
inflammation and infection of the diverticula causes by fecal blockages
What is Cholelithiasis?
Accumulation of gallstones
What is Cholecystitis?
Inflammation of the Gall bladder
What is cirrhosis?
Irreversible chronic degenerative disease
What is hepatitis?
Liver inflammation
What are hemorrhoids?
Varicose, dilated veins in anal canal
What are polyps?
Precancerous lesions
What do the islets of langerhans secrete?
These pancreatic cells secrete hormones such as glucagon or insulin
Which organ removes bilirubin from the blood, manufactures many of the plasma proteins, and is concerned with the production of clotting factors?
Liver
