Chapter 7- Digestion

Question 1

What is an example of controlled secretion by nervous and hormonal mechanisms?

Answer 1

Gastric juices

The volume and content of gastric secretion

Question 2

How does the secretion of gastric juices work?

Answer 2

Sight and smell of food causes the brain so send nerve impulse via the vagus never from the medullla- gland cells in the stomach walls are stimulated to secrete components of gastric juice

Question 3

Where do Exocrine glands secrete to?

Answer 3

salivary glands, the pancreas , gland cells in the stomach wall and the wall of the small intestine

To the surface of the body or the lumen of the gut

Question 4

What do exocrine glands secrete into?

Answer 4

Ducts - secretary cells are in groups around the duct brunch- each group of cells is called an acinus

Question 5

What do exocrine glands secrete

Answer 5

Saliva
Gastric juices
Pancreatic juice

Question 6

Structure of exocrine gland?

Answer 6

1) endoplasmic reticulum for syntheses of enzymes
2) mitochondria to provide ATP for protein synthesis and other cell activity
3) large number of secretory vesicles containing enzymes

Question 7

The inner surface of the ileum has numerous folds- each of the folds is covered in tiny projections called villi- where does absorption take place??

Answer 7

Through the epithelial cells covering each villus

Question 8

Each epithelial cell covering the villus adheres to its neighbours through tight junctions- what does this ensure?

Answer 8

That most materials pas into the blood vessels lining of the villi through the epithelial cell

Question 9

The cell surface membrane on the intestinal lumen side has a number of extensions called the micro villi- what is the collection of micro villi on the intestinal side of the epithelial cells calledV what do they do?

Answer 9

The brush border

Function is to increase the surface area for absorption

Question 10

What is the adaption of the epithelial cells regarding ATP

Answer 10

High amounts of ATP are needed to drive active transport - so epithelial cells have large numbers of mitochondria

Question 11

Adaption of pinocytic vesicles (regards to epithelial adaptions)

Answer 11

Often present in large numbers due to absorption of some foods by endocytosis

Question 12

What is the surface facing the lumen of the intestine referred to as? And the surface facing the blood vessels referred to as? What do they do?

Answer 12

Apical surface
Basal surface
Have different types of proteins involved in material transport

Question 13

How and who discovered the role of gastric acids in digestion?

Answer 13

William Beaumont while observing the process of digestion in an open wound caused by a gun shot

Question 14

What is acid secret by in the stomach?

Answer 14

The parietal cells

Question 15

What does acid inthe stomach do?

Answer 15

Disrupts the extracellular matrix that holds cells together in tissues- it also leads to the denaturing of proteins, exposing the polypeptide chains so that enzyme pepsin can hydrolyse the bonds within peptides

Pepsin is released by chief cells in inactive pepsingon- acid condition me in stomach convert inactive pepsingon into pepsin- ensures that the cells that produce pensinogen are not digested at the same time as the protein in the diet

Question 16

What are stomach ulcers caused by?

Answer 16

Open sores, caused by partial digestion of the stomach lining by the enzyme pepsin and hydrophilic acid in gastric juices - bacteria helicobacter shown to be more significant cause

Question 17

Why is stomach acid bad sometimes?

Answer 17

Several diease conditions made worse by release of acid- stomach acid is corrosive so the body produces a natural mucus barrier which protects the lining of the stomach being attacked by the acid- and some people this barrier may be broken down allowing the acid to damage the stomach and cause bleeding- known as a ulcer

Question 18

Other caused by stomach acids rather than just ulcer?

Answer 18

In others they may be a problem with the circular muscle at the top of the stomach that prevents fluid from escaping stomach- If the muscle is not functioning the acid escapes and irritates they oesophagus- this is called ‘acid reflux’ which can cause a symptom called heartburn

Question 19

What is a production of the acidic environment in the stomach achieved by?

Answer 19

A proton pump- this pump uses one ATP molecule to exchange two protons from the cytoplasm for two potassium ions in the lumen- one therapy is prescribed proton pump inhibitors for gastric disease

Question 20

What happens to materials that are not absorbed?

Answer 20

Egested

Question 21

What are the excretory products and what are they egested as?

Answer 21

Water and undigested dietary fibres are egested as feces

Question 22

What wre the two categories of dietary fibres?

Answer 22

Soluble and insoluble

Question 23

Why does a healthy balanced diet contain fibre?

Answer 23

As it increases the bulk of material passing through the intestines and helps to prevent constipation as it draws water into the intestine

The higher the water content of the intestine the quicker the movement of fecal matter

Question 24

What are other benefits of fibre in the diet?

Answer 24

Risk of various diseases of the large intestine may be reduced, including bowel cancer, hemorrhoids and appendicitis

Question 25

Causes of cholera

Answer 25

Caused by infection by the bacterium Vibrio Cholrea- releases toxin that binds to receptors on intestinal cells A toxin is then brought into the cell by endocytosis- toxin triggered cascade of results that leads to reflux of CL and HCO into intestines- leads to watery diarrhoea because water is drawn up to replace fluid lost in intestines - can result in death

Question 26

What do nervous and hormonal mechanisms control?

Answer 26

The secretion of digestive juices