Digestion I Study Guide Flashcards
sequence for the movement of food through the gastrointestinal tract
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
accessory organs
teeth, tongue, gallbladder, digestive glands
glands
salivary glands, liver, pancreas
Peristalsis
takes place during propulsion (moving food through GI tract), rhythmic waves of smooth muscle contraction – propels food through the GI tract
Segmentation
takes place during mechanical breakdown (chewing, mixing food with saliva, churning food), local contractions of the SI to mix food with digestive juices
digestion
series of catabolic steps in which enzymes break complex food molecules into their chemical building blocks
Absorption
passage of digested fragments from the lumen of the GI tract into blood/lymph
Peritoneum
robust serous membranes of the abdominopelvic cavity
- Visceral peritoneum: membrane on the external surface of most digestive organs
- Parietal peritoneum: membrane on the wall of the abdominal cavity
Peritoneal cavity
- Fluid filled space between the two peritoneum
- Fluid lubricates the mobile organs
Mesentery
a double layer of peritoneum – extends to the digestive organs from the abdominal walls
- Provides routes for blood vessels, lymphatics, and nerves
- Holds organs in place and stores fat
retroperitoneal organ
Organs located outside – posterior to – the peritoneum
layers/tunics of GI tract from most internal to external
Mucosa, submucosa, muscularis externa, serosa
Submucosa
consists of areolar connective tissue, contains blood and lymphatic vessels, lymphoid follicles and a nerve plexus. Has an abundant number of elastic fibers to help organs regain their shape after storing a large meal
Serosa
- Outermost, superficial layer
- Same as the visceral peritoneum
- Formed from areolar connective tissue covered with mesothelium – a single layer of squamous epithelium
- Replaced by fibrous adventitia in the esophagus
- Retroperitoneal organs have BOTH an adventitia and a serosa
Muscularis externa
- Muscle layer responsible for segmentation and peristalsis
- Contains an inner, circular muscle layer and an outer, longitudinal muscle layer
- The circular layer occasionally thickens to form sphincters
- Sphincters: act as valves to prevent backflow and control the passage of food
Mucosa
tunic layer that lines the lumen, a moist epithelial membrane
Functions:
- Secretes mucus, digestive enzymes, hormones
- Absorbs the end products of digestion
- Protects against infectious disease
3 sublayers of mucosa
epithelium, lamina propria, muscularis mucosae
Epithelium
most often a simple, columnar epithelium rich in mucus secreting cells
- The mouth, esophagus, anus are stratified, squamous
- Protects digestive organs from enzymes, eases food passage
- May create and secrete its own enzymes and hormones
Lamina Propria
loose, areolar connective tissue
- Contains lymphoid follicles to defend against microbes
- Rich supply of capillaries for nourishment and absorption
Muscularis Mucosae
very thin layer of smooth muscle
simple epithelium of GI tract
Stomach and intestines have simple columnar epithelium
stratified epithelium in the GI tract
The mouth, esophagus, anus are stratified, squamous
How many layers of muscularis exist in the stomach? How is this different from the rest of the GI tract?
3 – Most of the body has 2
Sphincter
act as valves to prevent backflow and control the passage of food (muscularis externa)
Is blood entering hepatic circulation rich or poor in Oxygen? How about nutrients?
- Collects nutrient-rich venous blood draining from the digestive viscera and brings it to the liver
- Enters oxygenated, leaves deoxygenated?
branch of the ANS that stimulates digestive activity
Parasympathetic nervous system
The GI tract’s own nervous system is called the
enteric nervous system
saliva
mostly water, and slightly acidic. It contains electrolytes, salivary amylase, mucin, lysozyme, urea, igA antibodies, and defensins
Major extrinsic salivary glands
produce most of the saliva, located outside oral cavity
- parotid, submandibular, sublingual
Parotid gland
anterior to the ear. External to the masseter; parotid duct to the oral vestibule
Submandibular gland
medial to the body of the mandible, duct to the base of lingual frenulum
Sublingual gland
anterior to the submandibular, opens to the floor of the mouth via 10-12 ducts
How many permanent, mature teeth are there?
32
Incisors
chisel shaped for cutting 8
Canines
fang-like for tearing, piercing 4
Premolars
broad crowns with rounded cusps, used to grind/crush 8
molars
broad crowns with rounded cusps, best for grinding 12
Wisdom teeth
3rd molars, emerge around 17-25 years of age
4
Where esophagus pierces through the diaphragm
Esophageal hiatus
sphincter on the proximal end of the stomach
gastroesophageal /cardiac sphincter (surrounds cardial orifice)
- Orifice is closed when food is not being swallowed
- Mucus cells on both sides of the sphincter help protect the esophagus from acid reflux
Heartburn
- Burning, radiating, substernal pain; mimics MI pain
- Cause: regurgitation of stomach acid into the esophagus
- First symptom of Gastroesophageal Reflux Disease (GERD)
- Increased risk with excessive intake of food/drink, obesity, pregnancy, running
- Frequent episodes -> esophagitis, esophageal ulcers
Hiatal hernia
- Structural abnormality caused by abnormal weakening of the gastroesophageal sphincter
- Superior portion of the stomach protrudes above the diaphragm
two phases of deglutination (swallowing)
buccal phase and pharyngeal-esophageal phase
Buccal phase
voluntary contraction of the tongue
pharyngeal-esophageal phase
involuntary phase driven by the vagus nerve; controlled in the swallowing centers of the medulla and lower pons, respiration is momentarily inhibited, and all undesired routes are blockers
