Digestive System

Question 1

Functions of dig tract

Answer 1

Ingestion
Motility
Secretion
Digestion
Absorption
Elimination

Question 2

define motility

Answer 2

voluntary + involuntary contractions to move materials thru the dig tract (overall term)

Question 3

Peristalsis

Answer 3

• circular smooth muscles contracting behind bolus (called peristaltic waves)
• followed by contraction of longitudinal *smooth** muscle
• triggered by hormones, chemicals, and physical stimulation

** (more specific than motility, and main function is to MOVE food)

Question 4

segmentation

Answer 4

• contraction of circular smooth muscle before + after bolus
• “chyme” now is mixed with dig secretions
• triggered by hormones, chemicals, + physical stimulation

** main function is to MIX food in one place, not move

Question 5

2 layers of peritoneum (a serous membrane)

Answer 5

parietal peritoneum: lines inner surface of abdo cavity (more superficial)

visceral peritoneum: cover external surface of some organs (deeper)

**space b/w the two layers is called peritoneal cavity (contains serous fluid)

Question 6

mesentaries

Answer 6

• folds (double layers) of the peritoneum, that suspend some organs
• contains blood + lymphatic vessels and nerves

Question 7

what is ascites

Answer 7

• abnormal fluid collection in the peritoneum
• often because of liver cirrhosis, heart/kidney failure, or some cancers

Question 8

what are intraperitoneal organs + examples

Answer 8

• WITHIN peritoneal cavity
• covered by the visceral peritoneum + suspended by mesentaries

examples: stomach, liver, jejunum (small intestine), etc

Question 9

what are retroperitoneal organs + examples

Answer 9

• lie OUTSIDE the peritoneal cavity
• located b/w the posterior layer of parietal peritoneum and the back
• only the anterior surface of the organ is covered by a peritoneum

examples: esophagus, pancreas, duodenum

Question 10

Four tunics of the digestive tract (outer to inner)

Answer 10

1. Serosa (aka visceral peritoneum)
2. Muscular layer (muscularis externa) –> 1 layers smooth muscle, except stomach has three!
3. Submucosa
4. Mucosa

Question 11

what is the serosa

Answer 11

• aka visceral peritoneum
• covers the external surfaces of INTRAperitoneal organs

Question 12

what is adventitia

Answer 12

• covers the external surfaces of RETROperitoneal organs
• when organ is retroperitoneal -> (fibrous CT layer that covers external surface of retroperitoneal organs

Question 13

what is the muscularis externa

Answer 13

• longitudinal muscle + circular (smooth muscle)
• mechanically processes + propels materials
• contains the enteric nervous system and myenteric plexus

Question 14

what is the submucosa (what type of connective tissue)

Answer 14

• layer of CT that plays key role in regulating dig secretions
• loose areolar CT
• also has submucosal plexus (nerves) + blood vessels!

Question 15

what is the mucosa (+ what type of membrane is it)

Answer 15

• innermost layer of the dig tract
• primary site of secretion + absorption, and protects underlying structures

type of membrane: simple columnar ET (bound to underlying lamina propria –> loose areolar CT) –> remember this is a mucus membrane

Question 16

Oral cavity (digestive function + type of ET)

Answer 16

dig function: ingestion, digestion, secretion, communication + expression

type of ET: keratinized stratified squamous epithelium

Question 17

what area the 3 salivary glands (+ function, waht it produces)

Answer 17

Parotid gland
Submandibular gland
Sublingual gland

• remember this a mixed multicellular EXOcrine gland

** all three produce saliva (helps start chem dig)

Question 18

saliva (what is it + function)

Answer 18

• serous + mucus secretions that start chemical dig
• includes water, electrolytes, mucus, leukocytes, and enzymes likes salivary amylase
• innervated by parasympathetic nervous system of ANS

Question 19

Pharynx (3 regions)

Answer 19

nasopharynx, oropharynx and laryngopharynx

Question 20

Esophagus

Answer 20

• from cricoid cartilage through esophageal hiatus into abdo cavity
• transitions from skeletal muscle to smooth muscle
• tissue type is mostly stratified squamous epithelium

Question 21

4 sphincters (+ what type of tissue, + function of each)

Answer 21

1. Lower esophageal sphincter (cardiac sphincter) : allows food into stomach
2. Pyloric sphincter: empties stomach content into small intestine
3. Ileocecal sphincter: small intestine contents into large intestine AND prevents backflow of bacterial contents of large intestine moving backwards
4. Internal anal sphincter: maintains continence (closed at rest), relaxes during defecation

** all are smooth muscle (involuntary)

Question 22

Stomach (functions)

Answer 22

• storage of food in prep for mechanical + chemical digestion
• stomach contents are called “chyme” not bolus anymore

rugae are specialized folds that allow stomach to extend w/ large meal

Question 23

stomach muscle layers (+ what type of epithelium in stomach)

Answer 23

stomach has simple columnar epithelium

3 muscle layers (outer to inner):
- longitudinal muscle layer (outer)
- circular muscle layer (middle)
- oblique muscle layer (inner)

Question 24

stomach’s secretory cells (mucous surface cells, and enteroendocrine cells) –> where are these found

Answer 24

cells are found in gastric pits –> simple columnar epithelium

mucous surface cells
- secretes mucin that forms mucus (protects ET from HCl, buffers the acid, protects from dig enzymes)

enteroendocrine cells
- endocrine cells that produce hormones (gastrin and somatostatin)

Question 25

what do the hormones gastrin and somatostatin do?

Answer 25

gastrin: stimulates parietal + chief cells to produce secretions somatostatin: regulatory hormone (inhibits gastrin, insulin, etc)

Question 26

what do parietal cells do

Answer 26

- secretes HCl - secretes intrinsic factor (needed for vit B12 absorption)

Question 27

what do chief cells do

Answer 27

- secretes pepsinogen (inactive protease) - activated when HCl is present

Question 28

what are enterochromaffin cells, what do they do

Answer 28

- secretes serotonin which helps regulate the enteric nervous system

Question 29

small intestine (functions + structures)

Answer 29

functions: digestion!!!, motility absorption, production of GI hormones + immune cells - has three segments (DJ ilium): Duodenum (shortest segment), Jejunum (max absorption here), Ileum (longest segment)

Question 30

what ET is small intestine made of + what other cells (+ their functions)

Answer 30

- simple columnar epithelium (aka enterocytes) --> site of nutrient absorption absorptive cells: produces dig enzymes goblet cells: produce mucus granular cells: immune protection endocrine cells: hormones like cholecystokinin (CCK) and secretin

Question 31

Small intestine (surface area, intestinal villi, lamina propria)

Answer 31

extensive surface area: to get max absorption intestinal villi: mucosal lining with microvilli lamina propria: contains lymphatic vells, blood capillaries, and **lacteals** (all help w/ absorption)

Question 32

What are the roles of plicae, villi, and microvilli in the small intestine?

Answer 32

All increase surface area for absorption: Plicae: folds of the small intestine wall Villi: finger-like projections of mucosa Microvilli: microscopic projections on enterocyte surfaces (brush border)

Question 33

what do capillary networks on villi do

Answer 33

absorb nutrients that enter hepatic portal vessels (small things)

Question 34

what do lacteals on villi do

Answer 34

absorb lipids + lipid sol molecules that enter lymphatic sys thru thoracic duct (big things)

Question 35

Where do nutrients absorbed in the capillaries of villi go?

Answer 35

Into the hepatic portal vein, which carries nutrient-rich blood from the small intestine to the liver

Question 36

What is absorbed by lacteals in the intestinal villi?

Answer 36

Lipids and lipid-soluble vitamins enter the lymphatic system, ultimately draining into the thoracic duct.

Question 37

What are the sources and order of blood flow in the liver?

Answer 37

Hepatic artery: oxygen-rich blood → central vein Hepatic portal vein: nutrient-rich blood from intestines → liver → central vein Flow sequence: hepatic portal vein → central vein → hepatic vein → inferior vena cava Significance: liver has first access to nutrients and toxins from the small intestine

Question 38

What are the main functions of the large intestine (colon)?

Answer 38

- Absorption of water (last chance), electrolytes, and vitamin K - Compaction of waste - Immune protection against pathogens

Question 39

How does epithelium change in the rectum and anus?

Answer 39

Simple columnar in rectum → stratified squamous at anus for abrasion protection

Question 40

What forms the structural framework of the liver?

Answer 40

Reticular connective tissue (CT) septa, which organizes liver tissue in 2D

Question 41

Key structural features of the large intestine?

Answer 41

Thinner walls, larger diameter than small intestine No villi Many goblet cells and some absorptive cells Lamina propria & submucosa contain lymphoid nodules (Peyer’s patches) Muscular layer reduced to taeniae coli, forming haustra

Question 42

What are the main functions of the liver?

Answer 42

Detoxification Metabolism regulation Bile production and secretion

Question 43

Name the lobes of the liver and outline bile flow.

Answer 43

Lobes: right, left, caudate, quadrate Bile flow: liver → bile → stored in gallbladder → released into duodenum.

Question 44

What types of muscle are present in rectum and anus, and how do sphincters work?

Answer 44

Internal anal sphincter: smooth muscle (involuntary) External anal sphincter: skeletal muscle (voluntary) Parasympathetic reflex: presence of stool relaxes the internal anal sphincter.

Question 45

What are hepatocytes and their roles?

Answer 45

Liver cells responsible for: Bile production Nutrient metabolism Detoxification

Question 46

hepatic artery

Answer 46

brings oxy blood (but less nutrients than hepatic veins) - drains into central vein

Question 47

hepatic portal vein

Answer 47

- carries nutrient rich blood from intestines to the liver for processing - first stop is the liver, with its super nutrient blood! - this is the one that is specifically rich in nutrients!!

Question 48

What makes up the portal triad in the liver?

Answer 48

Hepatic portal vein Hepatic artery Bile duct