Lecture #22 - GI system intro

Question 1

What is the primary function of the GI system?

Answer 1

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Question 2

Food —-> ingested ——> _______ ——essential for——> _______ ——-excretion of——-> _____

Answer 2

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Question 3

So the GI tract is a long tube from mouth to anus and it’s lined by what?
What are two modifications?

Answer 3

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Question 4

What are (from top to bottom) the 7 parts (well, 11 if you include the 4 parts of the Large Intestine) of the GI tract?

Answer 4

1. Oesophagus (25cm)
2. Stomach
3. Duodenum (26cm)
4. Jejunum and ileum (4 to 6cm)
5. Large intestine
   - ascending 15cm
   - transverse 45cm
   - descending 30cm
   - sigmoid 45cm
6. Rectum 12cm
7. Anus 4cm

Question 5

The outgrowths of the long tube - what is it and what are the four outgrowths?

Answer 5

Outgrowths = accessory organs (because tube not long enough to do all the job)

• salivary glands
• pancreas
• liver and gallbladder
• appendix

Question 6

4 main physiological functions of GI tract?

Answer 6

Motility
Secretion
Digestion
Absorption

Question 7

Physiological processes: motility

1. What are two patterns of movement and what’s used for control?
2. This contributes to which two processes?

Answer 7

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Question 8

Physiological processes: secretion

Need enzymes to breakdown food so it can be a_____

1. Occurs ____ the GI tract. What three things are secreted?
2. It involves what two parts of the body?
3. Essential for what process?

Answer 8

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Question 9

Physiological processes: digestion

1. Breaks down food to allow _____
2. What two kinds of processes are involved? So how do these processes occur?
3. Essential for what process?

Answer 9

2. Mechanical digestion from motility and chemical digestion from secretion of fluid and enzymes

Question 10

Physiological processes: absorption

1. Transport of material from where to where?
2. Occurs in what two parts of the GI tract? What’s absorbed in the respective parts?
3. Absorption is aided by what two processes?

Answer 10

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Question 11

Regulation

1. All processes must be _______
2. Regulation involves which three things what can you say about each?
3. Which of these has two systems and which is the primary neural system controlling GI function? So what does the other system do?

Answer 11

2. NERVOUS SYSTEM (has two - answered in Q3)
   HORMONES - regulation involves this
   CELLS in the lining epithelium - receptors (to detect when hormones present and start responding accordingly

Question 12

Continual movement along the gut tube - can’t get tangled so what’re two brief things that were mentioned that prevents this?

Answer 12

1. It’s held in place

2. Shiny/slipper so doesn’t tangle

Question 13

The structures of the gut in the abdomino-pelvic cavity are covered in what?

What does the mesentery contain/carry apart from its function of holding the structures in place and attaching to body wall, what other 3 things does it contain?

So what is the peritoneum (the peritoneal membrane): what kind of membrane? What cells? Under it? Over it? What does the “over it” do?

Answer 13

Mesentery contains/carries the vessels, nerves and fat (blood to and fro the gut itself)

Question 14

Important concept: when did the peritoneal membrane begin? When does the development of the accessory organs (outgrowths) start?

So the organs of the abdomen are surrounded by what cavity? What is this cavity covered with?

When organs grow and squash, there’s little space left of the peritoneal cavity and this little space left is called what?

Answer 14

During development

Peritoneal cavity and it’s covered with peritoneum.

Organs grow and squash and the little space left is called the potential cavity

Question 15

1. What does the visceral peritoneum cover?
2. What does the parietal peritoneum touch?
3. Which four organs are retroperitoneal? Why are they called retroperitoneal?

Answer 15

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Question 16

1. What is the mesentery?
   - double layer of what?
   - what’s outermost?
   - from body wall to?
2. What’s the omentum?
   - double layer of what?
   - what’s outermost?
   - from organ to what?

Answer 16

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Question 17

So the peritoneal cavity has potential space - if bacteria get in, what could happen?

Answer 17

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Question 18

Does the gut have lots of vasculature or not?

Answer 18

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Question 19

1. What major branch of the aorta supplies the foregut?
2. What major branch of the aroma supplies the midgut?
3. What major branch of the aroma supplies the hindgut?
4. How long is the gut with relation to length of body?
5. When does this pattern of the branches supplying to the different parts of the gut get set up?
6. “So celiac trunk is supplying region that’s developed from that length of the f_______”

Answer 19

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Question 20

What three vessels come off the celiac trunk?

Each of the three branches then supply three organs - what are they (except the last one supplies 4)

Answer 20

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Question 21

Superior mesenteric - what three branches?

What do each of these branches then supply to? Two each except last one is three

Answer 21

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Question 22

Inferior mesenteric - three branches

Each branch supplies to one except last one is to two

Answer 22

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Question 23

Why does the gut tube have so many blood vessels when it doesn’t need them?

Answer 23

Blood supplying forms a capillary network that’s very dense and we expect this venous blood to go into vena cava bit it doesn’t. It goes to liver and through the hepatic portal vein and empties into the cap network in liver (hepatic portal circulation). This is how we get our nutrients back to liver for storage, packaging, waste for excretion and drugs for metabolising. The blood could be toxic so important that goes back to liver (and then it goes to vena cava).