700 A&P

Question 1

The digestive system is composed of two main groups of organs

Answer 1

the digestive canal and accessory digestive organs.

Question 2

The digestive canal is a continuous tube extending from the esophagus to the anus.

Answer 2

The accessory digestive organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Question 3

Digestion includes six basic processes: ingestion, secretion, mixing and propulsion, mechanical and chemical digestion, absorption, and defecation.

Answer 3

Mechanical digestion consists of mastication and movements of the digestive canal that aid chemical digestion.

Chemical digestion is a series of hydrolysis reactions that break down large carbohydrates, lipids, proteins, and nucleic acids in foods into smaller molecules that are usable by body cells

Question 4

Layers of the Digestive Canal

Answer 4

The basic arrangement of layers in most of the digestive canal, from deep to superficial, is the

• mucosa
• submucosa
• muscular layer
• serosa

Question 5

The digestive canal is regulated by an intrinsic set of nerves known as the enteric nervous system (ENS) and by an extrinsic set of nerves that are part of the autonomic nervous system (ANS).

Answer 5

The ENS consists of neurons arranged into two plexuses: the myenteric neural plexus and the submucosal neural plexus

Question 6

Although the neurons of the ENS can function independently, they are subject to regulation by the neurons of the ANS

Answer 6

The myenteric neural plexus is located in the muscular layer, regulates digestive canal motility.

The submucosal neural plexus, which is located in the submucosa, regulates digestive canal secretion.

Question 7

Parasympathetic fibers of the vagus (X) nerves and pelvic splanchnic nerves increase digestive canal secretion and motility by increasing the activity of ENS neurons.

Answer 7

Sympathetic fibers from the thoracic and upper lumbar regions of the spinal cord decrease digestive canal secretion and motility by inhibiting ENS neurons.

Question 8

The peritoneum is the largest serous membrane of the body; it lines the wall of the abdominal cavity and covers some abdominal organs.

Answer 8

Folds of the peritoneum include the mesentery, mesocolon, falciform ligament, lesser omentum, and greater omentum

Question 9

The stomach connects the esophagus to the duodenum.

Answer 9

The principal anatomical regions of the stomach are the cardia, fundus, body, and pyloric part

Question 10

Adaptations of the stomach for digestion include gastric folds; glands that produce mucus, hydrochloric acid, pepsin, gastric lipase, and intrinsic factor; and a three-layered muscular layer.

Answer 10

Among the substances the stomach can absorb are water, certain ions, drugs, and alcohol

Question 11

The pancreas consists of a head, a body, and a tail and is connected to the duodenum via the pancreatic duct and accessory duct

Answer 11

Endocrine pancreatic islets secrete hormones, and exocrine pancreatic acini secrete pancreatic juice.

Pancreatic juice contains enzymes that digest

• starch (pancreatic amylase),
• proteins (trypsin, chymotrypsin, carboxypeptidase, elastase),
• triglycerides (pancreatic lipase)
• nucleic acids (ribonuclease and deoxyribonuclease)

Question 12

The liver has left and right lobes; the left lobe includes a quadrate lobe and a caudate lobe. The gallbladder is a sac located in a depression on the posterior surface of the liver that stores and concentrates bile.

Answer 12

The lobes of the liver are made up of lobules that contain hepatocytes (liver cells), sinusoids, stellate reticuloendothelial cells, and a central vein.

Question 13

Hepatocytes produce bile that is carried by a duct system to the gallbladder for concentration and temporary storage.

Bile’s contribution to digestion is the emulsification of dietary lipids.

Answer 13

The liver also functions in carbohydrate, lipid, and protein metabolism; processing of drugs and hormones; excretion of bilirubin; synthesis of bile salts; storage of vitamins and minerals; phagocytosis; and activation of vitamin D.

Question 14

The small intestine extends from the pyloric sphincter to the ileal orifice. It is divided into duodenum, jejunum, and ileum.

Answer 14

Its glands secrete fluid and mucus, and the circular folds, intestinal villi, and microvilli of its wall provide a large surface area for digestion and absorption.

Microvillous border enzymes digest α-dextrins, maltose, sucrose, lactose, peptides, and nucleotides at the surface of mucosal epithelial cells

Question 15

Digestive system includes six basic processes:

Answer 15

• Ingestion – introducing food into the alimentary canal
• Secretion – enzymes secreted along the GI tract to begin chemical breakdown
• Mixing and propulsion
• Chemical and mechanical digestion
• Absorption
• Defecation

Question 16

The GI tract is regulated by an intrinsic set of nerves know as the enteric nervous system (ENS) and by an extrinsic set of nerves that are a part of the ANS.

Answer 16

ENS
Myenteric plexus – regulates GI tract motility
Submucosal plexus – regulates GI secretion

Question 17

Principal anatomic regions of the stomach

Answer 17

Esophageal sphincter
Cardia
Fundus
Body
Pylorus
Pyloric sphincter
Oblique, 3rd layer of muscle

Question 18

Stomach connects the esophagus to the duodenum

Empty about 50 mL volume but can expand to 3-4L

Answer 18

3-4L of gastric juice produced daily

Converts bolus of food into paste like chyme

Question 19

stomach glands

Answer 19

Rugae – glands which produce mucus
Hydrochloric acid – released by parietal cells
Pepsin – released by chief cells
Gastric lipase – g-cell
 Intrinsic factor

Question 20

Pancreas

Answer 20

Consists of a head, body and a tail and is connected to the duodenum via the pancreatic duct and accessory duct

Question 21

Endocrine pancreatic islets secrete hormones and exocrine acini secrete pancreatic juice

Answer 21

-Pancreatic juice contains enzymes that digest starch (pancreatic amylase), proteins (trypsin, chymotrypsin, carboxypeptidase, and elastase), triglycerides (pancreatic lipase) and nucleic acids (ribonuclease and deoxyribonuclease)

Question 22

Liver Is composed of 4 lobes, 2 left and right

Answer 22

Lobes are made up of lobules that contain hepatocytes, sinusoids, stellate reticuloendothelial (Kupffer) cells and a central vein

Question 23

• Hepatocytes produce bile that is carried by a duct system to the Gallbladder for concentration and storage
• Bile emulsifies dietary lipids by allowing lipid digesting enzymes to digest and be absorbed

Answer 23

-Liver also functions in carbohydrate, lipid, and protein metabolism. Processes drugs and hormones. Excretes bilirubin. Stores vitamins and minerals, phagocytosis and activation of vitamin D

Question 24

Gallbladder

Answer 24

a sac located on the posterior surface of the liver that concentrates bile and secretes bile into the duodenum

Question 25

Small Intestine

Extends from the pyloric sphincter to the ileocecal sphincter, divided into three parts

Answer 25

Duodenum – chemical digestion
Jejunum – most nutrient absorption
Ileum – vitamins a, b, d, k absorbed

Question 26

The small intestine glands secrete fluid and mucus. The circular folds, villi and microvilli of its wall provide large surface area for digestion and absorption

Answer 26

• Mechanical digestion involves segmentation and migrating motility complexes
• Completes digestion of carbohydrates, proteins, and lipids, begins and completes digestion of nucleic acids
• Most of the nutrient absorption occurs in the small intestine. Absorption occurs via diffusion, facilitated diffusion, osmosis, and active transport.

Question 27

Large Intestine

Extends from the ileocecal sphincter to the anus

Answer 27

• Divided into the cecum, colon, rectum, and anal canal
• Mucosa contains many goblet cells and the muscularis consists of teniae coli and haustra
• Mechanical movements include haustral churning, peristalsis and mass peristalsis

Question 28

The last stages of chemical digestion occur in the large intestine through bacterial action

Answer 28

Substances are further broken down
Vitamins are synthesized
Water, ions and vitamins are absorbed

Question 29

Feces consists of water, inorganic salts, epithelial cells, bacteria, and undigested foods

Answer 29

Defecation is a reflex aided by voluntary contractions of the diaphragm and abdominal muscles, and relaxation of the external anal sphincter

Question 30

GI Summary what is released and what is absorbed

Answer 30

• Oral cavity – saliva amylase (enzyme) begin carbohydrate breakdown – no absorption
• Stomach – gastric juice, HCl-, pepsin (protein breakdown), intrinsic factor (helps absorption of B12) , gastrin (regulates HCl-) – can absorb alcohol, certain drugs

Question 31

GI Summary what is released and what is absorbed

Answer 31

• Liver – secretes bile
• Gallbladder – bile dilutes acid and emulsifies fat
• Pancreas – exocrine secretes pancreatic juice

Question 32

GI Summary what is released and what is absorbed

Answer 32

• Small intestine – secretes mucus electrolytes and water (lubricates and protects) – absorbs carbohydrates, vitamin B12 and small amounts of protein
• Large intestine – mucus secreted – water and salt absorbed, bacteria act on undigested material to be absorbed

Question 33

Energy Transfer
-Nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD) are coenxymes which carry hydrogen atoms during coupled oxidation-reduction actions

Answer 33

• Oxidation is the removal of electrons from a substance

- Reduction is the addition of electrons to a substance

Question 34

ATP can be generated three ways

Answer 34

Substrate level phosphorylation
Oxidative phosphorylation
Photophosphorylation