Exam 3 slides 3 Flashcards
List the accessory organs and glands
o Teeth, tongue, gallbladder, digestive glands
o Digestive Glands: salivary glands, liver, pancreas
Compare/contrast peristalsis and segmentation.
o Peristalsis: rhythmic waves of smooth muscle contraction – propels food through the GI tract
o Segmentation: local constrictions of the SI to mix food with digestive juices
What’s the difference in digestion and absorption?
o Digestion: series of catabolic steps in which enzymes break complex food molecules down into their chemical building blocks
o Absorption: passage of digested fragments from the lumen of the GI tract into blood/lymph
Define peritoneum, peritoneal cavity, and mesentery.
o 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
o Peritoneal Cavity
Fluid-filled space between the two peritoneum
Fluid lubricates the mobile organs
o 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
What does it mean to be a retroperitoneal organ?
o Retroperitoneal Organs: organs located outside – posterior to – the peritoneum
List the layers/tunics of GI tract. What are the functions/features of each layer? What are the 3 subdivisions within the mucosa?
o From the esophagus to the anus, the walls of the GI tract have the same 4 tunics:
o Mucosa
Tunic layer that lines the lumen, a moist epithelial membrane
3 Sublayers:
* Epithelium, Lamina Propria, Muscularis Mucosae
* Epithelium: most often a simple, columnar epithelium rich in mucus-secreting cells
o The mouth, esophagus, anus are stratified, squamous
o Protects digestive organs from enzymes, eases food passage
o May create and secrete its own enzymes and hormones
* Lamina Propria: loose, areolar connective tissue
o Rich supply of capillaries for nourishment and absorption
o Contains lymphoid follicles to defend against microbes
* Muscularis Mucosae: very thin layer of smooth muscle
Functions
* Secretes mucus, digestive enzymes, hormones
* Absorbs the end products of digestion
* Protects against infectious disease
o 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
o 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
o 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
o Each layer contains a predominant tissue type and plays a specific role
List the layers/tunics of GI tract
Mucosa
Submucosa
Muscularis externa
Serosa
What are the functions/features of each layer?
Mucosa
* Secretes mucus, digestive enzymes, hormones
* Absorbs the end products of digestion
* Protects against infectious disease
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
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
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
What are the 3 subdivisions within the mucosa?
- Epithelium, Lamina Propria, Muscularis Mucosae
- Epithelium: most often a simple, columnar epithelium rich in mucus-secreting cells
o The mouth, esophagus, anus are stratified, squamous
o Protects digestive organs from enzymes, eases food passage
o May create and secrete its own enzymes and hormones - Lamina Propria: loose, areolar connective tissue
o Rich supply of capillaries for nourishment and absorption
o Contains lymphoid follicles to defend against microbes - Muscularis Mucosae: very thin layer of smooth muscle
- Be familiar with the areas of stratified or simple epithelium in the GI tract.
How many layers of muscularis exist in the stomach? How is this different from the rest of the GI tract? What’s a sphincter?
3 layers
Longitudinal, circular, and oblique.
What branches of the aorta supply the abdominal viscera?
o Splanchnic Circulation: arteries that branch off the abdominal aorta to serve the digestive organs and hepatic portal circulation
o Typically, receives 1/4 of the heart’s CO – increases after a meal!
o Arterial Supply:
o Branches off the celiac trunk supply the spleen, liver, and stomach
o Mesenteric arteries supply the large and small intestines
o Hepatic Portal Circulation: collects nutrient-rich venous blood draining from the digestive viscera and brings it to the liver
Review hepatic portal circulation. Is blood entering hepatic circulation rich or poor in Oxygen? How about nutrients?
Hepatic Portal Circulation: collects nutrient-rich venous blood draining from the digestive viscera and brings it to the liver
Which branch of the autonomic nervous system stimulates digestive activity
parasympathetic nervous system
The GI tract’s own nervous system is called the: _________.
The GI tract’s own nervous system is called the: enteric nervous system.
Review the structures of the oral cavity listed on slide 19
o Associated Structures:
o Lips
o Cheeks
o Oral Vestibule
o Labial Frenulum
o Hard and Soft Palates
o Uvula
o Tongue
o Lingual Frenulum
o Lingual Tonsil
Know what is found in saliva and the locations of the 3 salivary glands + their ducts.
o Functions of Saliva:
o Cleanse the mouth
o Dissolve food chemicals for taste
o Moisten food, compact it into a bolus
o Begin breakdown of starch with the enzyme salivary amylase
o Saliva is mostly water and slightly acidic. It contains electrolytes, salivary amylase, mucin, lysozyme, urea, IgA antibodies, and defensins.
o Major (Extrinsic) Salivary Glands: produce most of the saliva, located outside the oral cavity
o Parotid: anterior to the ear, external to the masseter; parotid duct to the oral vestibule
o Submandibular: medial to body of the mandible; duct to the base of lingual frenulum
o Sublingual: anterior to the submandibular; opens to the floor of the mouth via 10-12 ducts
o Minor Salivary Glands: scattered throughout oral cavity
How many permanent, mature teeth are there? Be familiar with the locations and functions of the different types of mature teeth within the mouth.
o Teeth lie in sockets in the gum-covered margins of the mandible and the maxilla
o Mastication: the process of chewing – tearing and grinding food into smaller fragments
o Dentitions (Sets of Teeth)
20 deciduous (milk/baby) teeth - erupt between 6 and 24 months of age
32 deep-lying, permanent teeth
o About 6-12 years of age, permanent teeth enlarge and develop while the roots of the milk teeth are reabsorbed from below – milk teeth loosen and fall out
o Except for the 3rd molars (wisdom teeth), all permanent teeth are in by the end of adolescence
3rd molars emerge around 17-25 years of age
o Types of Teeth
Incisors: chisel shaped for cutting
Canines: fang-like for tearing, piercing
Premolars (Bicuspids): broad crowns with rounded cusps, used to grind/crush
Molars: broad crowns with rounded cusps, best for grinding
o In mastication, the upper and lower molars lock together and create a tremendous crushing force (~150 psi)
Where does the esophagus pierce through the diaphragm? Name the sphincter on the proximal end of the stomach? Review the clinical connection associated with this sphincter.
o Flat, muscular tube that runs from laryngopharynx to stomach – collapses when not in use
o Pierces through the diaphragm at the esophageal hiatus
o Joins the stomach at the cardial orifice
o Gastroesophageal/Cardiac Sphincter surrounds the 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
What are the two phases of deglutination? Which of these phases is voluntary?
o Two Phases:
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 blocked
o Solid foods pass from oropharynx to stomach in ~8s; fluids pass in ~1-2s