Digestive System Flashcards
function of the digestive system
mechanical digestion: breaks food down without altering chemical composition
chemical digestion: breaks food into simpler chemicals
ingestion, propulsion, absorption, defecation
the 4 layers of the wall of the alimentary canal
- mucosa - formed of surface epithelium, underlying connective tissue, and a small amount of smooth muscle.
- submucosa - contains considerable loose connective tissue as well as glands, blood vessels, lymphatic vessels, and nerves. nourish the surrounding tissues and carry away absorbed materials.
- muscular layer provides movements of the tube, consists of two coats of smooth muscle tissue
- serosa - outer layer covering the tube, functions in protecting underlying tissue and secreting serous fluid, which moistens and lubricates the tube’s outer surface so the organs slide freely against one another
4 accessory organs to digestion
salivary glands - 3 major pair produce and empty saliva into mouth by ducts for the purpose of moistening and binding food together to make chewing and swallowing easier - also produce amylase to begin digestion of complex carbohydrates
pancreas - pancreatic juices contain enzymes that digest carbohydrates, fats, protein, and nucleic acids.
liver - oxidizes fatty acids at an especially high rate, metabolizes carbs, lipids, proteins, stores some substances, filters blood, destroys toxins, secretes bile.
gallbladder - stores bile between meals
3 pairs of salivary glands
parotid glands - anterior to and partially inferior to the ears, between the skin of the cheeks and the masseter muscles - secretion is clear, watery serous fluid, rich in salivary amylase
submandibular glands - in the floor of the mouth, on the inside surface of the mandible. secrets some serous fluid with some mucus, more viscous than parotid secretion
sublingual glands - floor of mouth, inferior to tongue (but above submandibular) - thick, stringy mucous.
4 types of teeth
incisor - sharp chisel shaped bite off large pieces of food - front 4 teeth on top & bottom
canine - cone shaped, grasp and tear food - two on top & bottom
premolar & molar - flat surfaces for grinding food particles
4 regions of stomach
cardia: small area near esophageal opening
fundus: balloons superior to the cardia - temporary storage area and sometimes fills with swallowed air
body: main part of stomach, between fundus and pylorus
pylorus: funnel-shaped portion that narrows and becomes the pyloric canal as it approaches the small intestine.
2 openings of the stomach & their valves
lower esophageal sphincter remain contracted and close the entrance to the stomach to prevent regurgitation of stomach contents into esophagus.
pyloric sphincter: valve that controls gastric empting
6 organs of the alimentary canal
mouth - mechanical breakdown of food, begins chemical digestion of complex carbs
pharynx - connects mouth with esophagus
esophagus - peristalsis pushes food to stomach
stomach - secrets acid & enzymes, mixes food with secretions to begin enzymatic digestion of proteins
small intestine - mixes food with bile and pancreatic juice, final enzymatic breakdown of food molecules, main site of nutrient absorption
large intestine - absorbes water & electrolytes to form feces
rectum - regulates elimination of feces
3 regions of the small intestine
receives secretions from pancreas and liver, completes digestion of the nutrients in chyme, absorbs products of digestion, transports residue to large intestine
duodenum - most fixed portion of the small intestine, follows a C shaped path
jejunum & ileum - no distinct separation between jejunum and ileum, but diameter of jejunum is usually greater, and its wall is thicker, more vascular, and more active than that of the ileum.
ileum has more lymph nodes and a higher baterial population
9 regions of the colon
absorbes water and electrolytes, makes poo, breaks down things not broken down in the small intestine (like cellulose)
cecum appendix ascending colon transverse colon descending colon sigmoid colon rectum anal canal anus
4 lobes of the liver
major lobes:
larger right lobe
smaller left lobe
minor lobes
quadrate lobe - near gallbladder
caudate lobe - near inferior vena cava
ducts connecting the accessory organs to the small intestine
R & L hepatic ducts become the common hepatic duct, which joins w/ the cystic duct to become the bile duct
Steps in the swallowing mechanism
- soft palate is elevated preventing food from entering nasal cavity
- hyoid bone and larynx are elevated and the epiglottis closes to prevent food from entering the respiratory tract
- tongue is pressed against the soft palate to force food into the posterior part of the oral cavity and keep it from re-entering the oral cavity
- longitudinal muscles in the pharynx contract pulling the pharynx upward toward the food while inferior constrictor muscles relax to open esophagus
- superior constrictor muscles contract and force food into esophagus
Difference between deciduous and permanent teeth
deciduous - erupt between 6 months and 4 years. no premolars, no third molar
permanent - come in around 6 years
buccal cavity
this is the mouth
cheeks
hold food in mouth, muscles chew food
epiglottis
prevents food from entering the larynx
frenulum
connects midline of tongue to the floor of the mouth
gingiva
gums
hard & soft palate
muscles draw soft palate and uvulva upward which closes the opening between the nasal cavity and the pharynx, preventing food from entering the nasal cavity
lingual tonsils
rounded masses of lymphatic tissue that cover the root of the tongue, posterior to and behind the tongue
lip
judge temperature and texture of foods
palatine tonsils
help protect the body against infection (where tonsil stones are)
papillae
rough projections of the tongue which provide friction and helps handle food. also contains most of the taste buds
pharyngeal tonsils
behind soft palate, may be removed if enlarged
tongue body
mix food particles with saliva during chewing and move food toward the pharynx during swallowing