Exam 3 slides 3

Question 1

List the accessory organs and glands

Answer 1

o Teeth, tongue, gallbladder, digestive glands
o Digestive Glands: salivary glands, liver, pancreas

Question 2

Compare/contrast peristalsis and segmentation.

Answer 2

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

Question 3

What’s the difference in digestion and absorption?

Answer 3

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

Question 4

Define peritoneum, peritoneal cavity, and mesentery.

Answer 4

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

Question 5

What does it mean to be a retroperitoneal organ?

Answer 5

o Retroperitoneal Organs: organs located outside – posterior to – the peritoneum

Question 6

List the layers/tunics of GI tract. What are the functions/features of each layer? What are the 3 subdivisions within the mucosa?

Answer 6

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

Question 7

List the layers/tunics of GI tract

Answer 7

Mucosa
Submucosa
Muscularis externa
Serosa

Question 8

What are the functions/features of each layer?

Answer 8

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

Question 9

What are the 3 subdivisions within the mucosa?

Answer 9

• 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

Question 10

• Be familiar with the areas of stratified or simple epithelium in the GI tract.

Question 11

How many layers of muscularis exist in the stomach? How is this different from the rest of the GI tract? What’s a sphincter?

Answer 11

3 layers
Longitudinal, circular, and oblique.

Question 12

What branches of the aorta supply the abdominal viscera?

Answer 12

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

Question 13

Review hepatic portal circulation. Is blood entering hepatic circulation rich or poor in Oxygen? How about nutrients?

Answer 13

Hepatic Portal Circulation: collects nutrient-rich venous blood draining from the digestive viscera and brings it to the liver

Question 14

Which branch of the autonomic nervous system stimulates digestive activity

Answer 14

parasympathetic nervous system

Question 15

The GI tract’s own nervous system is called the: _________.

Answer 15

The GI tract’s own nervous system is called the: enteric nervous system.

Question 16

Review the structures of the oral cavity listed on slide 19

Answer 16

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

Question 17

Know what is found in saliva and the locations of the 3 salivary glands + their ducts.

Answer 17

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

Question 18

How many permanent, mature teeth are there? Be familiar with the locations and functions of the different types of mature teeth within the mouth.

Answer 18

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)

Question 19

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.

Answer 19

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

Question 20

What are the two phases of deglutination? Which of these phases is voluntary?

Answer 20

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