A&P 23: The Digestive System Flashcards
Digestive System
system that takes in food, breaks it down into nutrient molecules, absorbs these molecules into the bloodstream, then rids the body of the indigestible remains
Alimentary canal
GI tract; gut; continuous muscular tube that winds through the body from the mouth to the anus
Digests
breaks food down into smaller fragments
Absorbs
take in digested fragments through the lining of the GI tract into the blood
Accessory digestive organs
teeth, tongue, gallbladder, salivary glands, liver, pancreas
Ingestion
taking food into the digestive tract, usually via the mouth
Propulsion
moves food through the alimentary canal, includes swallowing (initiated voluntarily), peristalsis (involuntary; major means of this)
Mechanical breakdown
increases the surface area of ingested food, physically preparing it for digestion by enzymes; includes chewing, mixing food with saliva by the tongue, churning food in the stomach, and segmentation
Segmentation
rhythmic local constrictions of the small intestine
Digestion
involves a series of catabolic steps in which enzymes secreted into the lumen/cavity of the alimentary canal break down complex food molecules to their chemical building blocks
Absorption
passage of digested end products (plus vitamins, minerals, and water) from the lumen of the GI tract through the mucosal cells by active or passive transport into the blood or lymph
Defecation
eliminates indigestible substances from the body via the anus in the form of feces
Gut brain
consists of enteric nerves plexuses spread like chicken wire along the entire length of the GI tract and regulates digestive activity all along the tract
Peritoneum
most extensive of the serous membranes of the abdominopelvic cavity
Visceral peritoneum
covers the external surfaces of most digestive organs; continuous with the parietal peritoneum
Parietal peritoneum
lines the wall of the abdominopelvic cavity
Peritoneal cavity
area between the 2 peritoneums; a slitlike potential space containing a slippery fluid secreted by the serous membranes; lubricates the mobile digestive organs, allowing them to glide easily across one another and along the body wall as they carry out their activities
Mesentery
double layer of peritoneum that extends to the digestive organs from the body wall; provide routs for blood vessels, lymphatics, and nerves to reach the digestive viscera, hold organs in place, and store fat; mostly dorsal
Retroperitoneal organs
pancreas, duodenum, and parts of the large intestine are considered this type of organ based on their location in the abdominopelvic cavity; lose mesentery during development
Intraperitoneal/peritoneal organs
digestive organs like the stomach that keep their mesentery and remain in the peritoneal cavity
Peritonitis
inflammation of the peritoneum
Splanchnic circulation
includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation
Mucosa (mucous membrane)
innermost layer; moist epithelial membrane that lines the alimentary canal lumen from mouth to anus; major functions are to secrete mucus, digestive enzymes, and hormones, absorb the end products of digestion into the blood, and protect against infectious disease
Epithelium
except for that of the mouth, esophagus, and anus, where it is stratified squamous, this layer of the mucosa is simple columnar, rich in mucus-secreting cells
Lamina propia
layer underlying the epithelium; loose areolar connective tissue
MALT
mucosa-associated lymphoid tissue; help defend us against bacteria and other pathogens
Muscularis mucosae
external to the lamina propia is this scant layer of smooth muscle cells that produces local movements of the mucosa
Submucosa
layer just external to the mucosa; areolar connective tissue containing a rich supply of blood and lymphatic vessels, lymphoid follicles, and nerve fibers which supply the surrounding tissues of the GI tract wall
Muscularis externa (muscularis)
layer surrounding the submucosa; responsible for segmentation and peristalsis; has an inner circular layer and an outer longitudinal layer of smooth muscle cells
Serosa
outermost layer of the intraperitoneal organs; = visceral peritoneum; in most alimentary canal organs, formed of areolar connective tissue covered with mesothelium (single layer of squamous epithelial cells)
Adventitia
in the esophagus, the serosa is replaced by this ordinary fibrous connective tissue, which binds the esophagus to surrounding structures; retroperitoneal organs have both a serosa (on the side facing the peritoneal cavity) and this (on the side abutting the dorsal body wall)
Enteric neurons
neurons that staff the alimentary canal; communicate widely with one another to regulate digestive system activity
Submucosal nerve plexus
nerve network occupying the submucosa
Myenteric nerve plexus
nerve network lying between the circular and longitudinal muscle layers of the muscularis externa
Mouth
oral/buccal cavity; bounded anteriorly by the lips, laterally by the cheeks, superiorly by the palate, and inferiorly by the tongue
Oral orifice
anterior opening of the mouth
Lips (labia) & cheeks
help keep food between the teeth when we chew; composed of a core of skeletal muscle covered externally by skin; orbicularis oris, buccinators
Oral vestibule
recess bounded externally by the lips and cheeks and internally by the gums and teeth
Oral cavity proper
area that lies within the teeth and gums
Labial frenulum
median fold that joins the internal aspect of each lip to the gum
Palate
forms the roof of the mouth; has 2 distinct parts - hard and soft
Hard palate
underlain by the palatine bones and the palatine processes of the maxillae; forms a rigid surface against which the tongue forces food during chewing
Soft palate
mobile fold formed mostly of skeletal muscle that rises reflexively to close off the nasopharynx when we swallow
Palatoglossal arches
soft palate is anchored to the tongue by this
Palatopharyngeal arches
soft palate is anchored to the wall of the oropharynx by these more posterior folds
Fauces
the palatopharyngeal arches form the boundaries of this arched area of the oropharynx that contains the palatine tonsils
Uvula
fingerlike structure that projects downward from the free edge of the soft palate
Tongue
structure occupying the floor of the mouth; composed of interlacing bundles of skeletal muscle fibers; during chewing, it grips the food and constantly repositions it between the teeth
Bolus
compact mass formed by the tongue mixing food with saliva
Intrinsic muscles
muscles confined in the tongue; not attached to bone; their muscle fibers run in several different planes, allowing the tongue to change its shape (but not its position), becoming thicker, thinner, longer, or shorter as needed for speech and swallowing
Extrinsic muscles
muscles extending to the tongue from their points of origin on bones of the skull or soft palate; alter the tongue’s position - protrude it, retract it, and move it from side to side
Lingual frenulum
fold of mucosa that secures the tongue to the floor of the mouth and limits posterior movements
Filiform papillae
conical projections that roughen the tongue surface, helping us lick semisolid foods (like ice cream) and providing friction for manipulating foods; smallest and most numerous type; align in parallel rows on the tongue dorsum; contain keratin, which stiffen them and gives the tongue its whitish appearance
Fungiform papillae
mushroom-shaped projections scattered widely over the tongue surface; each has a vascular core that gives it a reddish hue
Vallate papillae
10-12 of these projections are located in a V-shaped row at the back of the tongue; resemble fungiform papillae but have an additional surrounding furrow
Foliate papillae
pleatlike structures located on the lateral aspects of the posterior tongue
Terminal sulcus
immediately posterior to the vallate papillae is this groove that distinguishes the portion of the tongue that lies in the oral cavity (its body) from its posterior portion in the oropharynx (its root)
Saliva
mouth secretion that cleanses the mouth, dissolves food chemicals so they can be tasted, moistens food and helps compact it into a bolus, and contains enzymes that begin the chemical breakdown of starchy foods
Major/extrinsic salivary glands
most saliva is produced by these glands that lie outside the oral cavity and empty their secretions into it
Minor/intrinsic salivary glands
buccal glands and others scattered throughout the oral cavity mucosa; slightly augment the output of saliva
Parotid gland
large, roughly triangular gland that lies anterior to the ear between the masseter muscle and the skin; its prominent duct parallels the zygomatic arch, pierces the buccinators muscle, and opens into the vestibule next to the 2nd upper molar
Submandibular gland
gland the size of a walnut; lies along the medial aspect of the mandibular body; duct runs beneath the mucosa of the oral cavity floor and opens at the base of the lingual frenulum
Sublingual gland
small, almond-shaped gland that lies anterior to the submandibular gland under the tongue and opens via 10-20 ducts into the floor of the mouth
Serous cells
cells that produce a watery secretion containing enzymes, ions, and a tiny bit of mucin
Mucous cells
cells that produce mucus
Mucus
stringy, viscous solution
Salivatory nuclei
when we ingest food, chemoreceptors and mechanoreceptors in the mouth send signals to these nuclei in the brain stem (pons and medulla); as a result, parasympathetic nervous system activity increases
Teeth
lie in sockets (alveoli) in the gum-covered margins of the mandible and maxilla
Primary dentition
milk/baby teeth
Permanent dentition
deep-lying teeth; usually 32 in a full set
Incisors
chisel-shaped teeth adapted for cutting or nipping off pieces of food
Canines
conical or fanglike teeth; AKA cuspids or eyeteeth that tear and pierce
Premolars
bicuspids; grind/crush
Molars
broad crowns with rounded cusps for grinding/crushing; during chewing, upper and lower ones repeatedly lock together, an action that generates tremendous crushing forces
Dental formula
shorthand way of indicating the numbers and relative positions of the different types of teeth
Crown
enamel-covered, exposed part of the tooth
Gingiva
gum; surrounds the tooth like a tight collar
Enamel
brittle ceramic-like material thick as a dime; directly bears the force of chewing; hardest substance in the body; heavily mineralized with calcium salts
Root
portion of the tooth embedded in the jawbone; canines, incisors, and premolars have one of these; 1st 2 upper molars have 3; corresponding lower ones have 2
Neck
constricted tooth region; connects the crown and root
Cement
calcified connective tissue; covers the outer surface of the root and attaches the tooth to the thin periodontal ligament
Periodontal ligament
ligament that anchors the tooth in the bony socket of the jaw, forming a fibrous joint called a gomphosis
Dentin
protein-rich bonelike material, underlies the enamel cap and forms the bulk of the tooth; acts as a shock absorber during biting and chewing
Pulp cavity
dentin surrounds this area that contains a number of soft tissue structures (connective tissue, blood vessels, and nerve fibers)
Pulp
soft tissue structures within the pulp cavity
Root canal
where the pulp cavity extends into the root, it becomes this
Apical foramen
at the proximal end of each root canal is this hole that allows blood vessels, nerves, and other structures to enter the pulp cavity
Odontoblast
each tubule contains this elongated process; “tooth former”; cell type that secretes and maintains the dentin
Dental caries
cavities; result from bacterial action that gradually demineralizes enamel and underlying dentin
Dental plaque
decay begins when this film of sugar, bacteria, and other mouth debris) adheres to the teeth
Calculus
calcified dental plaque; tartar
Gingivitis
gum infection
Periodontal disease
periodontitis; when gingivitis worsens and bacteria cause neutrophils and immune system cells to carve deep pockets around the teeth; accounts for 80-90% of tooth loss in adults
Oropharynx, laryngopharynx
common passageways for food, fluid, and air
Esophagus
muscular tube about 25cm long and is collapsed when not involved in food propulsion
Esophageal hiatus
the esophagus pierces the diaphragm at this point to enter the abdomen
Cardial orifice
the esophagus joins the stomach at this point within the abdominal cavity
Gastroesophageal/cardiac sphincter
the cardial orifice is surrounded by this sphincter
Heartburn
the 1st symptom of GERD; burning, radiating substernal pain that occurs when stomach acid regurgitates into the esophagus
Hiatal hernia
heartburn is common in those with this condition, a structural abnormality (most often due to abnormal relaxation or weakening of the gastroesophageal sphincter) in which the superior part of the stomach protrudes slightly above the diaphragm
Mastication
chewing
Deglutition
swallowing
Buccal phase
phase of swallowing that occurs in the mouth and is voluntary
Pharyngeal-esophageal phase
phase of swallowing controlled by the swallowing center located in the brain stem (medulla and lower pons); involuntary
Stomach
temporary “storage tank” where chemical breakdown of proteins begin and food is converted to a creamy paste
Chyme
creamy paste that food is converted to at the beginning of chemical breakdown of proteins
Rugae
large, longitudinal folds that the stomach collapses into when empty