A&P 23: The Digestive System Flashcards
(268 cards)
1
Q
Digestive System
A
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
2
Q
Alimentary canal
A
GI tract; gut; continuous muscular tube that winds through the body from the mouth to the anus
3
Q
Digests
A
breaks food down into smaller fragments
4
Q
Absorbs
A
take in digested fragments through the lining of the GI tract into the blood
5
Q
Accessory digestive organs
A
teeth, tongue, gallbladder, salivary glands, liver, pancreas
6
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Ingestion
A
taking food into the digestive tract, usually via the mouth
7
Q
Propulsion
A
moves food through the alimentary canal, includes swallowing (initiated voluntarily), peristalsis (involuntary; major means of this)
8
Q
Mechanical breakdown
A
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
9
Q
Segmentation
A
rhythmic local constrictions of the small intestine
10
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Digestion
A
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
11
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Absorption
A
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
12
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Defecation
A
eliminates indigestible substances from the body via the anus in the form of feces
13
Q
Gut brain
A
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
14
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Peritoneum
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most extensive of the serous membranes of the abdominopelvic cavity
15
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Visceral peritoneum
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covers the external surfaces of most digestive organs; continuous with the parietal peritoneum
16
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Parietal peritoneum
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lines the wall of the abdominopelvic cavity
17
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Peritoneal cavity
A
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
18
Q
Mesentery
A
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
19
Q
Retroperitoneal organs
A
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
20
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Intraperitoneal/peritoneal organs
A
digestive organs like the stomach that keep their mesentery and remain in the peritoneal cavity
21
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Peritonitis
A
inflammation of the peritoneum
22
Q
Splanchnic circulation
A
includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation
23
Q
Mucosa (mucous membrane)
A
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
24
Q
Epithelium
A
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
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Lamina propia
layer underlying the epithelium; loose areolar connective tissue
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MALT
mucosa-associated lymphoid tissue; help defend us against bacteria and other pathogens
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Muscularis mucosae
external to the lamina propia is this scant layer of smooth muscle cells that produces local movements of the mucosa
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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
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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
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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)
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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)
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Enteric neurons
neurons that staff the alimentary canal; communicate widely with one another to regulate digestive system activity
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Submucosal nerve plexus
nerve network occupying the submucosa
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Myenteric nerve plexus
nerve network lying between the circular and longitudinal muscle layers of the muscularis externa
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Mouth
oral/buccal cavity; bounded anteriorly by the lips, laterally by the cheeks, superiorly by the palate, and inferiorly by the tongue
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Oral orifice
anterior opening of the mouth
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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
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Oral vestibule
recess bounded externally by the lips and cheeks and internally by the gums and teeth
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Oral cavity proper
area that lies within the teeth and gums
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Labial frenulum
median fold that joins the internal aspect of each lip to the gum
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Palate
forms the roof of the mouth; has 2 distinct parts - hard and soft
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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
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Soft palate
mobile fold formed mostly of skeletal muscle that rises reflexively to close off the nasopharynx when we swallow
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Palatoglossal arches
soft palate is anchored to the tongue by this
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Palatopharyngeal arches
soft palate is anchored to the wall of the oropharynx by these more posterior folds
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Fauces
the palatopharyngeal arches form the boundaries of this arched area of the oropharynx that contains the palatine tonsils
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Uvula
fingerlike structure that projects downward from the free edge of the soft palate
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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
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Bolus
compact mass formed by the tongue mixing food with saliva
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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
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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
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Lingual frenulum
fold of mucosa that secures the tongue to the floor of the mouth and limits posterior movements
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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
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Fungiform papillae
mushroom-shaped projections scattered widely over the tongue surface; each has a vascular core that gives it a reddish hue
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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
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Foliate papillae
pleatlike structures located on the lateral aspects of the posterior tongue
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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)
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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
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Major/extrinsic salivary glands
most saliva is produced by these glands that lie outside the oral cavity and empty their secretions into it
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Minor/intrinsic salivary glands
buccal glands and others scattered throughout the oral cavity mucosa; slightly augment the output of saliva
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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
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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
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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
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Serous cells
cells that produce a watery secretion containing enzymes, ions, and a tiny bit of mucin
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Mucous cells
cells that produce mucus
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Mucus
stringy, viscous solution
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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
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Teeth
lie in sockets (alveoli) in the gum-covered margins of the mandible and maxilla
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Primary dentition
milk/baby teeth
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Permanent dentition
deep-lying teeth; usually 32 in a full set
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Incisors
chisel-shaped teeth adapted for cutting or nipping off pieces of food
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Canines
conical or fanglike teeth; AKA cuspids or eyeteeth that tear and pierce
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Premolars
bicuspids; grind/crush
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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
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Dental formula
shorthand way of indicating the numbers and relative positions of the different types of teeth
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Crown
enamel-covered, exposed part of the tooth
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Gingiva
gum; surrounds the tooth like a tight collar
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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
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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
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Neck
constricted tooth region; connects the crown and root
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Cement
calcified connective tissue; covers the outer surface of the root and attaches the tooth to the thin periodontal ligament
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Periodontal ligament
ligament that anchors the tooth in the bony socket of the jaw, forming a fibrous joint called a gomphosis
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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
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Pulp cavity
dentin surrounds this area that contains a number of soft tissue structures (connective tissue, blood vessels, and nerve fibers)
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Pulp
soft tissue structures within the pulp cavity
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Root canal
where the pulp cavity extends into the root, it becomes this
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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
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Odontoblast
each tubule contains this elongated process; "tooth former"; cell type that secretes and maintains the dentin
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Dental caries
cavities; result from bacterial action that gradually demineralizes enamel and underlying dentin
90
Dental plaque
decay begins when this film of sugar, bacteria, and other mouth debris) adheres to the teeth
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Calculus
calcified dental plaque; tartar
92
Gingivitis
gum infection
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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
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Oropharynx, laryngopharynx
common passageways for food, fluid, and air
95
Esophagus
muscular tube about 25cm long and is collapsed when not involved in food propulsion
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Esophageal hiatus
the esophagus pierces the diaphragm at this point to enter the abdomen
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Cardial orifice
the esophagus joins the stomach at this point within the abdominal cavity
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Gastroesophageal/cardiac sphincter
the cardial orifice is surrounded by this sphincter
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Heartburn
the 1st symptom of GERD; burning, radiating substernal pain that occurs when stomach acid regurgitates into the esophagus
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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
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Mastication
chewing
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Deglutition
swallowing
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Buccal phase
phase of swallowing that occurs in the mouth and is voluntary
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Pharyngeal-esophageal phase
phase of swallowing controlled by the swallowing center located in the brain stem (medulla and lower pons); involuntary
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Stomach
temporary "storage tank" where chemical breakdown of proteins begin and food is converted to a creamy paste
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Chyme
creamy paste that food is converted to at the beginning of chemical breakdown of proteins
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Rugae
large, longitudinal folds that the stomach collapses into when empty
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Cardial part (cardia)
part of the stomach near the heart; surrounds the cardial orifice through which food enters the stomach from the esophagus
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Fundus
stomach's dome-shaped part, tucked beneath the diaphgram that bulges superiorly to the cardia
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Body
midportion of the stomach
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Pyloric part
funnel-shaped portion of the stomach; is continuous with the body
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Pyloric antrum
wider and more superior area of the pyloric part
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Pyloric canal
pyloric antrum narrows to form this part of the stomach
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Pylorus
pyloric canal terminates at this part
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Pyloric sphincter/valve
the pylorus is continuous with the duodenum through this part, which controls stomach emptying
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Greater curvature
convex lateral surface of the stomach
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Lesser curvature
concave medial surface of the stomach
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Lesser omentum
mesentery that helps tether the stomach to other digestive organs and the body wall; runs from the liver to the lesser curvature of the stomach, where it becomes continuous with the visceral peritoneum covering the stomach
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Greater omentum
drapes inferiorly from the greater curvature of the stomach to cover the coils of the small intestine; wraps the spleen and the transverse portion of the large intestine before blending with the mesocolon (dorsal mesentery that secures the large intestine to the parietal peritoneum of the posterior abdominal wall)
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Gastric pits
smooth lining of the stomach mucosa is dotted with millions of these
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Gastric glands
gastric glands lead into these tubular glands that produce the stomach secretions
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Gastric juice
stomach's secretions
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Mucous neck cells
cells scattered in the neck and more basal regions of the glands produce a thin, soluble mucus quite different from that secreted by the mucous cells of the surface epithelium
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Parietal cells
cells found mainly in the more apical region of the glands scattered among the chief cells; simultaneously secrete HCl and intrinsic factor
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Pepsin
protein-digesting enzyme; HCl makes the stomach contents extremely acidic, a condition necessary for activation and optimal activity of this enzyme
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Chief cells
occur mainly in the basal regions of the gastric glands; cuboidal ones produce pepsinogen (inactive form of pepsin)
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Enteroendocrine cells
cells typically located deep in the gastric glands; release a variety of chemical messengers directly into the interstitial fluid of the lamina propia
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Histamine, serotonin
chemical messengers that act locally as paracrines
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Somatostatin
chemical messenger that act both as paracrines locally and as hormones that diffuse into the blood capillaries to influence several digestive system target organs
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Gastrin
hormone that plays essential roles in regulating stomach secretion and motility
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Mucosal barrier
thick coating of bicarbonate rich mucus builds up on the stomach wall, the epithelial cells of the mucosa are joined together by tight junctions that prevent gastric juice from leaking into the underlying tissue layers, & damaged epithelial mucosal cells are shed and quickly replaced by division of undifferentiated stem cells that reside where the gastric pits join the gastric glands -- in these ways, the stomach protects itself
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Peptic ulcers
persistent damage to the underlying tissues can promote these
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Gastric ulcers
erosions of the stomach wall that cause gnawing epigastric pain
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Rennin
an enzyme that acts on milk protein (casein), converting it to a curdy substance that looks like soured milk
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Intrinsic factor
required for intestinal absorption of vitamin B12, needed to produce mature erythrocytes
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Cephalic (reflex) phase
phase of gastric secretion occurring before food enters the stomach; a few minutes long, this phase is triggered by the aroma, taste, sight, or thought of food, and it gets the stomach ready for its upcoming digestive chore
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Gastric phase
once food reaches the stomach, local neural and hormonal mechanisms initiate this phase of gastric secretion; lasts 3-4 hours and provides about 2/3 of the gastric juice released
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G cells
gastrin-secreting enteroendocrine cells in the stomach antrum
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Alkaline tide
as H+ is pumped from the cell & HCO3- (bicarbonate) accumulates within the cell, HCO3- is ejected through the basolateral cell membrane into the capillary blood; as a result, the blood draining from the stomach is more alkaline than the blood serving it
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Intestinal phase
phase of gastric secretion with 2 components - stimulatory and inhibitory
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Intestinal (enteric) gastrin
hormone that encourages the gastric glands to continue their secretory activity
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Enterogastric reflex
inhibitory trio of reflexes that (1) inhibit the vagal nuclei in the medulla, (2) inhibit local reflexes, & (3) activate sympathetic fibers that cause the pyloric sphincter to tighten and prevent further food entry into the small intestine
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Enterogastrones
intestinal hormones, including secretin, cholecystokinin (CCK), & vasoactive intestinal peptide (VIP); all inhibit gastric secretion when the stomach is very active
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Receptive relaxation
response of smooth muscle in the stomach fundus and body which occurs both in anticipation of and in response to food moving through the esophagus and into the stomach
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Gastric accommodation
example of smooth muscle plasticity; intrinsic ability of visceral smooth muscle to exhibit the stress-relaxation response (can stretch without greatly increasing its tension)
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Basic electrical rhythm (BER)
cyclic slow waves of the stomach
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Vomiting (emesis)
unpleasant experience that empties the stomach by a different route
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Emetic center
part of the medulla that initiates a number of motor responses preceding vomiting
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Small intestine
body's major digestive organ; digestion is completed here and virtually all absorption occurs here
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Ileocecal valve (sphincter)
where the small intestine joins the large intestine
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Duodenum
mostly retroperitoneal part of the small intestine; relatively immovable; curves around the head of the pancreas; about 25cm long; shortest division of the small intestine
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Hepatopancreatic ampulla
bulblike point where the bile duct and the main pancreatic duct unite in the wall of the duodenum
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Major duodenal papilla
the hepatopancreatic ampulla opens into the duodenum via this volcano-shaped structure
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Hepatopancreatic sphincter
smooth muscle valve that controls the entry of bile and pancreatic juice into the duodenum
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Jejunum
2.5m long part of the small intestine; central part
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Ileum
3.6m long part of the small intestine; distal part; joins the large intestine at the ileocecal valve
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Circular folds
deep, permanent folds of the mucosa and submucosa of the small intestine; 1cm tall; force chime to spiral through the lumen, slowing its movement and allowing time for full nutrient absorption
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Villi
fingerlike projections of the mucosa, over 1mm high; give it a velvety texture; large and leaflike in the duodenum, gradually narrow/shorten along the length of the small intestine
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Lacteal
in the core of each villus is a dense capillary bed and this wide lymphatic capillary where digested foodstuffs are absorbed through the epithelial cells into both it & the capillary blood
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Microvilli
exceptionally long, densely packed structures of the absorptive cells of the mucosa; gives the mucosal surface a fuzzy appearance
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Brush border
fuzzy appearance of the mucosal surface of the small intestine
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Brush border enzymes
the plasma membranes of the microvilli bear enzymes referred to as this, which complete the digestion of carbohydrates and proteins in the small intestine
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Intestinal crypts
between the villi, the mucosa is studded with pits leading into these tubular glands in the small intestine
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Peyer's Patches
aggregated lymphoid nodules in the small intestine; primarily located in the lamina propria but occasionally protrude into the submucosa; increase in abundance toward the distal end of the small intestine
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Duodenal glands
elaborate, mucus-secreting glands in the submucosa of the duodenum; produce an alkaline (bicarbonate-rich) mucus that helps neutralize acidic chime moving in from the stomach
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Liver
largest gland in the body; occupies most of the hypochondriac and epigastric regions, extending farther to the right of the body midline than to the left; lies almost entirely within the rib cage; has 4 primary lobes
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Falciform ligament
mesentery; separates the right and left lobes anteriorly and suspends the liver from the diaphragm and anterior abdominal wall
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Round ligament/ligamentum teres
runs along the inferior edge of the falciform ligament; fibrous remnant of the fetal umbilical vein
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Hepatic artery & hepatic portal vein
vessels entering the liver at the porta hepatis & the common hepatic duct
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Porta hepatis
gateway to the liver
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Common hepatic duct
bile leaves the liver through several bile ducts that ultimately fuse to form this large duct, which travels downward toward the duodenum
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Cystic duct
common hepatic duct fuses with this duct to form the bile duct
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Bile duct
fusion of common hepatic duct and cystic duct
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Liver lobules
structural & functional units of the liver
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Hepatocytes
liver cells; organized like bricks in a garden wall
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Central vein
hepatocyte plates radiate outward from this vessel, running in the longitudinal axis of the lobule
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Portal triad
at each of the 6 corners of a liver lobule is this portal tract region, AKA ___; contains 3 basic structures - branch of the hepatic artery (supplying oxygen-rich arterial blood to the liver), a branch of the hepatic portal vein (carrying venous blood laden with nutrients from the digestive viscera), & a bile duct
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Liver sinusoids
between the hepatocyte plates are enlarged, heavily fenestrated ___ _____
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Stellate macrophages
hepatic macrophages; form part of the sinusoid walls; star-shaped; remove debris (e.g. bacteria) and worn-out blood cells from the blood as it flows past
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Bile canaliculi
tiny canals which bile flows through; run between adjacent hepatocytes toward the bile duct branches in the portal triads
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Hepatitis
inflammation of the liver; most often due to viral infection; 6 viruses cause it, A-F
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Cirrhosis
progressive chronic inflammation of the liver that typically results from severe chronic hepatitis or chronic alcoholism; damaged hepatocytes regenerate but the liver's connective/scar tissue regenerates faster; liver becomes fatty and fibrous, depressing its activity
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Portal hypertension
condition that results when scar tissue in the liver obstructs blood flow throughout the hepatic portal system
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Bile
yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, triglycerides, phospholipids (lecithin and others), and a variety of electrolytes; only bile salts & phospholipids aid the digestive process
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Bile salts
primarily cholic and chenodeoxycholic acids; cholesterol derivatives; role = to emulsify fats; also facilitate fat and cholesterol absorption; help solubilize cholesterol, both that contained in bile and that entering the small intestine in food
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Bilirubin
chief bile pigment; waste product of the heme of hemoglobin formed during the breakdown of worn-out erythrocytes
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Gallstones
biliary calculi; painful crystals caused by too much cholesterol or too few bile salts allowing the cholesterol to crystalize; obstructs the flow of bile from the gallbladder; pain radiates to the right thoracic region when the gallbladder or its duct contracts (from the sharp crystals)
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Pancreas
soft, tadpole-shaped gland that extends across the abdomen from its tail (abutting the spleen) to its head, which is encircled by the C-shaped duodenum; most of this organ is retroperitoneal; deep to the greater curvature of the stomach
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Pancreatic juice
exocrine produce produced by the pancreas; drains from the pancreas into the duodenum via the centrally located main pancreatic duct
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Main pancreatic duct
duct from which pancreatic juice drains
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Acini
clusters of secretory acinar cells surrounding ducts; full of RER and exhibit deeply staining zymogen granules
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Zymogen granules
deeply staining particles containing inactive digestive enzymes (proenzymes) they manufacture
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Enteropeptidase
intestinal brush border protease within the duodenum; formerly called enterokinase; activates trypsinogen to trypsin
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Trypsin
activates trypsinogen and 2 other pancreatic proteases (procarboxypeptidase & chymotrypsinogen) to their active forms
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Carboxypeptidase
active form of procarboxypeptidase
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Chymotrypsin
active form of chymotrpysinogen
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Amylase, lipases, nucleases
other pancreatic enzymes; secreted in active form; require that ions or bile be present in the intestinal lumen for optimal activity
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Migrating motor complex (MMC)
each successive peristaltic wave of the small intestine begins a bit more distally; this pattern of peristaltic activity is called this
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Gastroileal reflex
long reflex triggered by stomach activity; increases the force of segmentation in the ileum & relaxes the sphincter
200
Large intestine
organ framing the small intestine on 3 sides & extending from the ileocecal valve to the anus
201
Feces
waste eliminated from the body as a semisolid
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Teniae Coli
"ribbons of the colon" 3 bands of smooth muscle = longitudinal muscle layer of the large intestine
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Haustra
teniae coli puckers the wall of the colon into these pocketlike sacs
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Epiploic appendages
small fat-filled pouches of visceral peritoneum that hang from the surface of the large intestine; significance unknown
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Cecum
saclike "blind pouch" which lies below the ileocecal valve in the right iliac fossa; 1st part of the large intestine
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Appendix
attached to the posteromedial surface of the cecum is this blind, wormlike structure; contains masses of lymphoid tissue; part of MALT; important role in body immunity; storehouse of bacteria, recolonizes the gut when needed
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Appendicitis
acute inflammation of the appendix; results from a blockage (often by feces) that traps infectious bacteria in its lumen
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Colon
another name for the large intestine; several distinct regions
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Ascending colon
part of the large intestine that travels up the right side of the abdominal cavity to the level of the right kidney
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Right colic (hepatic) flexure
right-angle turn by the ascending colon
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Transverse colon
part of the large intestine that travels across the abdominal cavity
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Left colic (splenic) flexure
directly anterior to the spleen, the large intestine bends acute and descends down the left side of the posterior abdominal wall
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Descending colon
part of the large intestine that travels down the left side of the posterior abdominal wall
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Sigmoid colon
part of the large intestine that enters the pelvis and becomes S-shaped
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Mesocolons
mesentery sheets that anchors the transverse and sigmoid colon to the posterior abdominal wall
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Rectum
in the pelvis, at the level of the 3rd sacral vertebra, the sigmoid colon joins this structure, which runs posteroinferiorly just in front of the sacrum
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Rectal exam
digital (finger) examination of the pelvic organs through the anterior rectal wall
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Rectal valves
3 transverse folds that stop feces from being passed along with gas (flatus)
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Anal canal
last segment of the large intestine; lies in the perineum, entirely external to the abdominopelvic cavity
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Anus
where the rectum opens to the body exterior
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Internal anal sphincter
involuntary sphincter composed of smooth muscle (part of the muscularis)
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External anal sphincter
voluntary sphincter composed of skeletal muscle
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Anal columns
mucosa of the anal canal hangs in these long ridges/folds
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Anal sinuses
recesses between the anal columns; exude mucus when compressed by feces, which aids in emptying the anal canal
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Bacterial flora
live bacteria entering the cecum from the small intestine (most are dead) + bacteria that enter the GI tract via the anus; 10 million discrete types; functions = colonize the colon, synthesize B complex vitamins and some of the vitamin K the liver needs to produce several clotting proteins, metabolize some host-derived molecules (mucin, heparin, and hyaluronic acid), & ferment some of the indigestible carbohydrates (cellulose, xylan, & others), releasing irritating acids and a mixture of gases (dimethyl sulfide, H2, N2, CH4, & CO2)
226
Haustral contractions
movements seen most in the colon; slow, segmenting movements lasting about 1 minute that occur every 30 minutes or so; occur mainly in the ascending/transverse colon, reflect local controls of smooth muscle within the walls of the individual hasutra
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Mass movements
mass peristalsis; long, slow-moving, powerful contractile waves that move over large areas of the colon 3-4 times daily and force the contents toward the rectum; typically occur during or just after eating
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Gastrocolic reflex
propulsive reflex that forces contents of the colon toward the rectum
229
Diverticula
small herniations of the mucosa through the colon walls
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Diverticulosis
condition where the diverticula herniate through the mucosa of the colon walls; most commonly occurs in the sigmoid colon; affects over half of people over age 70
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Diverticulitis
in 20% of cases, diverticulosis progresses to this condition in which the diverticula become inflamed and may rupture, leaking into the peritoneal cavity, which can be life threatening; foods and products that make feces bulkier help prevent this condition
232
Defecation reflex
when mass movements force feces into the rectum, stretching of the rectal wall initiates this reflex
233
Diarrhea
watery stools; result from any condition that rushes food through the large intestine before that organ has had sufficient time to absorb the remaining water; causes include irritation of the colon by bacteria, prolonged physical jostling of the digestive viscera (occurs in marathon runners)
234
Constipation
too much water is absorbed when food remains in the colon for extended periods and the stool becomes hard and difficult to pass; may result from lack of fiber in the diet, improper bowel habits (failing to the heed the "call"), lack of exercise, emotional stress, or laxative abuse
235
Digestion
catabolic process that breaks down large food molecules to monomers (chemical building blocks) small enough to be absorbed by the GI tract lining
236
Hydrolysis
enzymatic breakdown of any food molecule; involves adding a water molecule to each molecular bond to be broken/lysed
237
Monosaccharides
simple sugars; monomers of carbohydrates; glucose, fructose, and galactose are common in our diet
238
Salivary amylase
substance present in saliva; splits starch into oligosaccharides (smaller fragments of 2-8 linked glucose molecules); works best in a slightly acid to neutral environment (6.75-7) maintained in the mouth by the buffering effects of bicarbonate and phosphate ions in saliva
239
Pancreatic amylase
starchy foods and other digestible carbs that escape being broken down by salivary amylase are acted on by this enzyme in the small intestine
240
Dextrinase & glucoamylase
most important brush border enzymes; act on oligosaccharides composed of more than 3 simple sugars
241
Maltase, sucrase, lactase
simple sugars; hydrolyze maltose, sucrose, and lactose into their constituent monosaccharides
242
Amino acid
healthy individuals digest much protein all the way to these monomers
243
Pepsin
protein digestion begins in the stomach when pepsinogen secreted by the chief cells is activated to this group of protein-digested enzymes; activated by high pH in the duodenum
244
Rennin
enzyme that coagulates milk protein; not produced in adults
245
Trypsin & chmyotrypsin
proteolytic enzymes secreted by the pancreas that cleave the proteins into smaller peptides, which in turn become the grist for other enzymes
246
Carboxypeptidase
pancreatic and brush border enzyme that splits off 1 amino acid at a time from the end of the polypeptide chain that bears the carboxyl group
247
Aminopeptidase & dipeptidase
brush border enzymes that liberate final amino acid products; 1 works from the amine end of a protein, one amino acid at a time
248
Lipases
pancreas is the major source of these fat-digesting enzymes, which makes the small intestine the primary site of lipid digestion
249
Fatty acids and monoglycerides
glycerol with 1 fatty acid chain attached
250
Pancreatic nucleases
nuclei in pancreatic juices hydrolyze the nucleic acids to their nucleotide monomers
251
Nucleotides
monomers of nucleic acids
252
Nucleosidases & phosphates
intestinal brush border enzymes that break nucleotides apart to release their free bases, pentose sugars, and phosphate ions
253
Micelles
collections of fatty acid elements clustered together with bile salts in such a way that the polar (hydrophilic) ends of the molecule face the water and the nonpolar portions form the core
254
Chylomicrons
water-soluble lipoprotein drops
255
Lipoprotein lipase
enzyme associated with capillary endothelium
256
Ferritin
ionic iron, essential for hemoglobin production, is actively transported into the mucosal cells, where it binds to this protein; phenomenon = mucosal iron barrier
257
Transferrin
in the blood, iron binds to this plasma protein that transports it into circulation
258
Vitamin D
active form of this vitamin promotes active calcium absorption
259
Malabsorption
impaired nutrient absorption
260
Primitive gut
developing alimentary canal
261
Stomodeum
depressed area of the surface ectoderm
262
Oral membrane
anteriomost endoderm and stomodeum fuse to become this, which eventually becomes the opening of the mouth
263
Proctodeum
ectodermal depression
264
Cloacal membrane
"sewer"; fuses with the proctodeum to form the anus
265
Cleft palate
one of the most common congenital defects that interferes with feeding; palatine bones or palatine process of the maxillae (or both) fail to fuse; serious because causes child to be unable to suck properly
266
Cleft lip
one of the most common congenital defects; interferes with feeding because lip fails to form correctly
267
Gastroenteritis
inflammation of the GI tract
268
Cholecystitis
inflammation of the gallbladder
