Digestive System Pt. 2 - GI Tract

Question 1

What is the esophagus made of?

Answer 1

It is a tube made of smooth muscle

Question 2

Where are circular and longitudinal muscles located and what are they?

Answer 2

Circular muscles and longitudinal muscles are apart of the esophagus and they help push the bolus of food down the esophagus

Question 3

How do the circular muscles contracting help with pushing the bolus of food?

Answer 3

Contract to squeeze the lumen shut behind the bolus so it doesn’t move back up the esophagus

Question 4

How do the longitudinal muscles contracting help with pushing the bolus of food?

Answer 4

As the circular tube squeezes to close the lumen, the longitudinal muscles contract in a wave-like motion until it reaches the stomach

Question 5

Once the esophagus reaches the stomach what does it have to go through to reach the stomach and how does this structure work?

Answer 5

The esophagus needs to pass through the lower esophageal sphincter to get into the stomach

• Circular smooth muscle known as the cardiac sphincter and it responsible for closing once the food reaches the stomach

Question 6

What structures makes up the entire stomach?

Answer 6

Cardia, Fundus, Body and Pylorus

Question 7

Where are the lesser and greater curvature found?

Answer 7

Lesser curvature - concave medial border of the stomach
Greater curvature - convex lateral border of the stomach

Greater curvature is on the more inferior side

Question 8

Where is the fundus with respect to the other structures in the stomach?

Answer 8

Superior and left to the cardia and superior to the body

Question 9

What is the body of the stomach made of and what are they used for?

Answer 9

Made of muscular layers called:
1. Circular layer
2. Longitudinal layer
3. Oblique layer

Question 10

Summarize how mechanical breakdown works in the stomach

Answer 10

• Squeezing and crushing of bolus of food
• Three muscular layers of stomach (circular, longitudinal & oblique) contract and get a lot of crushing in stomach
• Bolus spends a lot of time in the stomach

Question 11

What is the pylorus section of the stomach split into?

Answer 11

1. Pyloric antrum
2. Pyloric canal
3. Pyloric sphincter

Question 12

What is the rugae of mucosa and where is it located?

Answer 12

Located on the inner wall and is lumpy and has pits called gastric glands

Question 13

Where are the pyloric antrum and canal located with respect to each and the stomach and what do they do?

Answer 13

They are both more distal located in the stomach and the pyloric antrum is located to the left of the pyloric canal (closer to the duodenum)

• Pyloric antrum - Connects to the body of the stomach
• Pyloric canal - leads to the third region known as the pylorus

Question 14

What is the pyloric sphincter?

Answer 14

Connects to the duodenum via the pylorus and is made of smooth muscle

Question 15

What are gastric glands?

Answer 15

Found within pits rugae of mucosa

• Different types of cells that produce something contributing to digestive stuff

Question 16

What are the surface mucous and mucous neck cell?

Answer 16

Most superficial gastric glands located near the top
* Produces mucus to break food chemically and assist mechanically

Question 17

What are parietal cells?

Answer 17

Deeper than surface and mucous neck cells and are responsible for secreting HCL & intrinsic factor to break proteins down

Note: Only area that has linings in the wall to withstand the HCl which is why when you vomit you feel an acidic feeling in your esophagus (lining cannot withstand it)

Question 18

Purpose of intrinsic factor in parietal cells of gastric glands

Answer 18

Helps absorb vit. B12 which is important for RBC function

Question 19

What are chief and G cells?

Answer 19

They are the deepest gastric gland cells which produce digestive enzymes

1. Chief cell - secretes pepsinogen & gastric lipase
2. G cells - secretes the hormone gastrin

Question 20

How does the Enteric Nervous System interact with the pyloric sphincter?

Answer 20

Once digestion is done the enteric nervous system sends signals to the pyloric sphincter to move food along to the duodenum

Question 21

What is the small intestine composed of?

Answer 21

Duodenum - found posterior to the stomach, 10 inches long and turns into the jejunum
Jejunum - central portion of the small intestine which is 3 feet long
Ileum - 6 feet long and the last portion of the small intestine

Question 22

How does the ileum connect to the cecum of the large intestine?

Answer 22

Through the ileocecal sphincter and it prevents food from going back up the small intestine

Question 23

Function of the small intestines include?

Answer 23

Absorption - need a lot of SA & blood

Question 24

What increases the SA in the small intestine

Answer 24

Villi and microvilli

• Villi are bumps with even littler bumps called microvilli

• Villi give big SA in a fairly compact space
• Villi contains tons of blood vessels and has a lot of cells (have microvilli on the cells)

Question 25

Walls of small intestine contain single layered epithelial cells and what is this used for?

Answer 25

• To allow diffusion of nutrients into the blood

Note: Nutrients in the blood are sent to the liver to be checked for toxins before sent to the cells of villi

Question 26

What is the function of the large intestine?

Answer 26

Water absorption and vitamin absorption

Question 27

From the cecum where does the chyme go?

Answer 27

Through the colons - ascending, transverse and finally colon

Question 28

What is the vermiform appendix and where is it located?

Answer 28

Attached to the posterior-medial portion of the cecum & is apart of the immune system

Note: Not necessary b/c other parts have immune function which is why it gets removed with a lot of people

Question 29

What is the right colic flexure?

Answer 29

Between the ascending and transverse colon where the chyme needs to take a sharp right turn

Liver is found right above it which is why a sharp turn is required

Question 30

What is the left colic flexure and where is it located?

Answer 30

Anterior to the spleen it is the part of the transverse colon where you must take a sharp turn into the descending colon

Question 31

What is the sigmoid colon?

Answer 31

The final colon of the digestive system and projects medially at the midline and terminates at the level of S3

Question 32

What structures are found inferior to the sigmoid colon?

Answer 32

Rectum, Anal Canal and Anus and this is where waste products from metabolising dumped into the large intestine get excreted

Question 33

Where is the rectum located with respect to the structures around it?

Answer 33

Between the sigmoid and the anal canal

Question 34

The anal canal has two muscles one of which is made of smooth muscle and the other skeletal. What are they?

Answer 34

• Internal anal sphincter is the involunatary smooth muscle that will open on it’s own when the rectum sends excrements down the anus
• External anal sphincter is the voluntary skeletal muscle connected to the levator ani muscle which we can control when to contract and open