The Digestive System
Terms in this set (94)
Provides the body with the nutrients, water, and electrolytes essential for health.
-The organs of this system ingest, digest, and absorb food and eliminate the undigested remains as feces.
hollow tube extending from the mouth to the anus, into which various accessory organs or glands empty their secretions.
-Mouth, pharynx, and
-Stomach, small intestine, and
large intestine (colon)
- Mucosa → Submucosa → Muscularis externa → Serosa
- Mechanical digestion - Chemical digestion
- Absorption - Defecation
serosa (serous membrane)
The walls of the ventral body cavity and the outer surfaces of the organs it contains are covered with an thin, double-layered membrane
the part of the membrane lining the cavity walls
part of the membrane covering the external surface of the organs within the cavity.
• These membranes produce a thin lubricating fluid that allows the viceral organs to slide over one another or to rub against the cavity wall without friction.
• They also compartmentalize the various organs so that infection of one organ is prevented from spreading to others.
the serosa lining the the abdominopelvic cavity and covering its organs.
surrounds digestive organs
lines the body wall
space between the visceral and parietal peritoneum that contains a lubricating serous fluid
-Holds organs in place
-Sites of fat storage
-Provides a route for circulatory vessels and nerves
a double layer of peritoneum...a sheet of two serous membranes fused back to back that extends to the digestive organs from the body wall.
two ventral mesenteries
binds the anterior aspect of the liver to the anterior abdominal wall and diaphragm
runs from the liver to the stomach and duodenum.
connects the greater curvature of the stomach to the posterior abdominal wall
sheet that fans interiorly from the posterior abdominal to support the jejunum and
holds transverse colon to posterior abdominal wall
connects sigmoid colon to posterior pelvic wall
Mucosa (mucous membrane)
innermost layer containing three sublayers: a) a lining epithelium, b) a lamina propria, and c) a muscularis mucosae
abuts the lumen of the alimentary canal and functions to absorb nutrients and secrete mucus.
a loose areolar or reticular C.T. that nourishes the lining epithelium and absorb digested nutrients.
- Contains MALT
thin layer of smooth muscle that produces local movements of the mucosa.
-Dislodges food particles that become embedded in the mucosa
a layer of C.T. containing major blood and lymphatic vessels and nerve fibers.
-Its vascular network sends branches to all other layers of the wall.
-Its C.T. is a "moderately dense" C.T....an intermediate between loose areolar and dense irregular C.T.
Muscularis externa (muscularis)
consists of two layers of smooth muscle that are responsible for peristalsis:
a) inner circular layer: squeezes the gut tube
b) outer longitudinal layer: shortens the gut tube
-In some places, the circular layer thickens to form sphincters that act as valves to prevent the backflow of food from one organ to the next.
Serosa (visceral peritoneum)
the protective outermost layer; areolar C.T. covered by single layer of squamous epithelial cells
Mouth (oral cavity)
where food enters the alimentary canal and is chewed, manipulated by the tongue, and moistened with saliva.
- Mucosa-lined cavity bounded by the lips, cheeks, palate, and the tongue.
- Posteriorly, the mouth borders the fauces of the oropharynx.
the slit between the
teeth and the cheeks (or lips).
Oral cavity proper
the region of the mouth that lies internal to the teeth.
Lips (labia) and cheeks
help keep food inside the mouth during chewing, are composed of a core of skeletal muscle covered by skin.
-thick flaps extending from the inferior boundary of the nose to the superior boundary of the chin.
the region of the lip where lipstick is applied...a transition zone where the skin meets the oral mucosa.
a median fold that connects the internal aspect of each lip to the gum
roof of the mouth
anterior bony part that forms a rigid surface against which the tongue forces food during chewing.
posterior muscular part that is a mobile flap that rises to close off the nasopharynx during swallowing
-anchored to the tongue by the palatoglossal arches and to the wall of the oropharynx by the palatopharyngeal arches.
projects downward from the free edge of the soft palate
-Grips food and constantly repositions it between the teeth.
- Mixes the food with salvia and form it into a compact mass called a bolus.
- During swallowing...the tongue moves posteriorly to push the bolus into the pharynx.
- Houses most of the tastebuds
- In speech, the tongue helps form some consonants (k, d, t, and l)
fold of mucosa on the undersurface of the tongue that both secures the tongue to the floor of the mouth and limits its posterior movements
give the tongue roughness and provide friction
scattered widely over the tongue and give it a reddish hue, contains taste buds
V-shaped row in back of tongue, contains taste buds
groove that separates the mouth and pharynx
tear and grind the food, breaking it into smaller fragments.
Primary denition (deciduous teeth)
20 total that erupt at intervals between 6 and 24 months
enlarge and develop causing the root of deciduous teeth to be resorbed and fall out between the ages of 6 and 12 years; all but the third molars ("wisdom teeth") have erupted by the end of adolescence; there are usually 32 permanent teeth
chisel-shaped teeth adapted for cutting or nipping
conical or fanglike teeth that tear or pierce
Premolars (bicuspids) and molars
have broad crowns with
rounded tips and are best suited for grinding or crushing
a) moisten, dissolves food, binds food together (bolus)
b) aids in digestion of starch
c) prevents tooth decay by neutralizing acids
d) contains bactericidal enzymes, antiviral substances, and
antibodies to kill harmful oral microorganisms
e) contains proteins to help growth of beneficial bacteria
compound (branched ducts) tubuloalveolar (secretory unit shape) glands
Intrinsic salivary glands
scattered within mucosa of tongue, palate, lips, and cheeks; keep mouth moist at all times
Extrinsic salivary glands
lie external to the mouth but have ducts that open to the mouth
oropharynx and laryngopharynx
allow passage of food and fluids to the esophagus and air to the trachea.
-Lined with stratified squamous epithelium and mucus glands
-Has two skeletal muscle layers; Inner longitudinal and outer pharyngeal constrictors
Muscular tube (~10 inches) that joins the laryngopharynx to the stomach; travels through the mediastinum and pierces the diaphragm; joins the stomach at the cardiac orifice
-The empty esophagus is folded longitudinally and flattened
-Glands secrete mucus as a bolus moves through the esophagus
-Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly)
Site where food is churned into chyme (the liquid substance found in the stomach; consists of partially digested food, water, hydrochloric acid, and various digestive enzymes). ~4 hours
- Protein digestion begins (Secretes pepsin)...functions under acidic conditions
- Some substances are absorbed through the stomach...water, electrolytes, and some drugs.
a strong acid that destroys many harmful bacteria in the food.
Cardiac region (cardia)
surrounds the cardiac orifice at the junction
with the esophagus
dome-shaped region immediately inferior to diaphragm
midportion of the stomach
made up of the antrum (cave) and canal which terminates at the pylorus; pylorus is continuous with the duodenum (1st part small intestine) through the pyloric sphincter
longitudinal folds of mucosa; allow distension
entire extent of the convex lateral surface
concave medial surface
Longest portion of the alimentary canal (short people: 2.7-5 meters, tall people: 6-7 meters).
-Site of most enzymatic digestion and absorption of nutrients. (~3-6 hours)
-Three subdivisions: duodenum (5%), jejunum (40%), and ileum (55%)
Receives digestive enzymes from the pancreas and bile from the liver and gallbladder.
-10 inches long
major duodenal papilla
ampulla opens into the duodenum
Main pancreatic duct and common bile duct enter the wall of the duodenum where they form a bulb
Circular folds (plicae circulares)
Force the chyme to spiral through the intestinal lumen...slowing its movement.
1 mm tall fingerlike projections of the mucosa that are covered by a simple columnar epithelium made up primarily of absorptive cells (enterocytes) specialized for absorbing digested nutrients.
-Contains lacteals and blood capillaries.
tiny projections of absorptive cell's at the apical surface that contain enzymes
- 200 m2
Contain an abundant amount of endoplasmic reticulum...assembles newly absorbed lipid molecules into lipid-protein complexes called chylomicrons, which enter the lacteal capillaries.
secrete mucus that lubricates chyme and forms a protective barrier that prevents enzymatic digestion of the intestinal wall.
cells of the duodenum that secrete hormones
signals the gallbladder to release stored bile and the pancrease to secrete its digestive enzymes
signals the pancreatic ducts to secrete a bicarbonate-rich juice to neutralize the acidic chyme entering the duodenum.
mucosa between the villi that contain epithelial cells that secrete intestinal juice...a watery liquid that mixes with chyme.
- Epithelial stem cells divide in the crypts and renew the mucosal epithelium by moving continuously into the villi.
and electrolytes (~12-24 hours).
-Digested residue contains few nutrients
-Small amount of digestion by bacteria
-Mass peristaltic movements force feces toward the rectum
three longitudinal strips, spaced at equal intervals around the circumference of the cecum and colon.
puckered sacs of the large intestine
fat-filled pouches of visceral peritoneum that hang from the intestine...no known function.
a pouch connected to the ileum and the ascending colon of the large intestine.
-It regulates the flow of chyme into the bowels.
- a sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine.
tube connected to the cecum; neutralizes pathogens.
-Removed: the appendix is a vestigial structure with no absolute purpose
storage tube for solid wastes. The main function of the colon appears to be extraction of water and salts from feces.
-Divided into distinct segments: Ascending, transverse, descending, and sigmoid colon
the final straight portion of the large intestine, terminating at the anus
the last subdivision of the large intestine. The external opening of the rectum.
-Digestive function...produces bile; an alkaline compound which aids in digestion, via the emulsification of lipids.
glycogen storage, decomposition of red blood cells,
plasma protein synthesis, and detoxification.
mesentery that separates the right and left lobes anteriorly and binds the liver to the anterior abdominal wall.
area near the center of the visceral surface where most of the major vessels and nerves enter and leave the liver.
-Thin-walled, green muscular sac on the ventral surface of the liver, stores and concentrates bile by absorbing its water and ions, releases bile via the cystic duct, which flows into the bile duct
Cystic duct, hepatic duct, and common bile duct
Bile, which is synthesized in the liver, is carried to the right and left hepatic ducts, which converge to form the common hepatic duct. There it enters the superior end of the common bile duct and either empties into the second part of the duodenum, or enters the cystic duct to be stored in the gallbladder.
Acinar cells make, store, and secrete pancreatic enzymes which are activated in the duodenum and breaks down food.
-Endocrine function: produces the hormones insulin and glucagon which regulates blood sugar
A duct joining the pancreas to the common bile duct to supply pancreatic juices which aid in digestion provided by the "exocrine pancreas".
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