Digestive physiology

Question 1

What are omnivores and carnivores more likely to be?

Answer 1

these are more likely to be monogastric

Question 2

What are herbivores most likely to have?

Answer 2

ruminants

Question 3

What does the pancreas do ?

Answer 3

It releases a vast array of pancreatic juices for digestion

Question 4

What are the components of the digestive tract?

Answer 4

Mouth
Esophagus
Stomach
The small intestine
Colon (large intestine)
Rectum
Through this process a number of enzymes act on the food we eat including the liver (releasing bile), pancreas and gall bladder.

Question 5

Can we break down beta glucose molecules?

Answer 5

We can only break down alpha glycosidic bonds using alpha amylases not beta bonds.

Question 6

Explain the processes occurring in each part of the digestive system?

Answer 6

The mouth and esophagus
In the mouth, saliva acts to start to break down carbohydrates using the enzyme amylase (some lipase). There is also an enzymes called lysozymes which are antibacterial. The esophagus is a tube, controlled by muscles and autonomic nerves, that helps food to travel from the mouth to the stomach.

The stomach
The stomach coats the food with a mixture of acid and digestive enzymes to help break the food down further. A layer of mucous protects the stomach lining from being damaged by the acid. (foveolar cells)
The bottom of the stomach is able to contract, which helps to speed up the process. When the food is broken down sufficiently the stomach releases its contents into the duodenum. (food now called chyne)

The small intestine
The small intestine is categorised in three parts; the duodenum being the first, the jejunum second and the ileum the final part.

When food enters the duodenum, the pancreas releases enzymes to help break down fat, protein and carbohydrate The gall bladder releases bile, which has been produced by the liver, to help further break fats down into a form that can be absorbed by the intestines.

The small intestine is lined with finger-like projections, called villi, which provide a very large surface area facilitating the absorption of nutrients, including carbohydrates, proteins and fats, into the bloodstream.
The small intestine also plays a key role in regulating blood glucose levels The small intestine contains a number of receptive cells which detect the presence of macronutrients and secrete hormones which instructs the pancreas on how much insulin and glucagon to release.

The colon (large intestine)
The final stage of the digestive system is the colon (large intestine) which absorbs water and salts before the remains are passed out of the rectum as faeces. The colon can also help to absorb remaining carbohydrate and some fats.

Question 7

What is the pylorus?

Answer 7

The part of the stomach that connects to the duodenum

Question 8

What are foveolar cells?

Answer 8

Foveolar cells or surface mucous cells are mucus-producing cells which cover the inside of the stomach, protecting it from the corrosive nature of gastric acid. These cells line the gastric mucosa.

Question 9

What are cheif cells and what do they do?

Answer 9

chief cells including the gastric chief cell and the parathyroid chief cell.

The gastric chief cell (also known as peptic cell) is a cell in the stomach that releases pepsinogen and chymosin. Pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with hydrochloric acid produced by gastric parietal cells.
This type of cell also secretes gastric lipase enzymes, which help digest triglycerides into free fatty acids and di- and mono-glycerides. Leptin has been found in the pepsinogen granules of chief cells.

The parathyroid chief cell is the primary cell of the parathyroid gland. It produces and secretes parathyroid hormone in response to low calcium levels. PTH plays an important role in regulating blood calcium levels by raising the amount of calcium in the blood.

Question 10

What are parietal cells?

Answer 10

Parietal cells are epithelial cells in the stomach that secrete hydrochloric acid (HCl) as H+ and Cl- so that they don’t digest themselves. These cells are located in the gastric glands found in the lining of the fundus and body regions of the stomach.

Question 11

What is the role of Brunner gland for digestion?

Answer 11

Brunner’s glands are located in the submucosa of the duodenum. They secrete an alkaline fluid containing mucin, which protects the mucosa from the acidic stomach contents entering the duodenum into the intestines

Question 12

What is the fundus?

Answer 12

The fundus is the top part of the stomach that stores gas from digestion. It can also hold food if the stomach becomes full.

Question 13

What are the parts of the small intestine?

Answer 13

the duodenum, jejunum, and ileum. They helps to further digest food coming from the stomach. They absorbs nutrients (vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be used by the body.

Question 14

What is the cecum?

Answer 14

A pouch that forms the first part of the large intestine. It connects the small intestine to the colon, which is part of the large intestine. This part includes very dense fibre-packed products and is where there is the largest diversity of microbes (bacteria) that break down fibres and beta-linked glucose molecules including things like cellulose. During this process they produce organic acids (volatile fatty acids VFA’s or SCFA’s) these can then be oxidised and used by colonocytes (epithelial cells) where they get 70% of their energy requirements and pass on energy to the rest of the body. They also produce vitamins.

Question 15

What happens to the size of the digestive system in more carnivorous organisms?

Answer 15

Meat is easily digested compared to plant material, the digestive system of a carnivore is typically shorter than a herbivore of comparable size.

Question 16

Explain the steps of food being broken down in ruminants

Answer 16

1. Mouth
   Cattle will graze and put grass in their mouth for mastication. They chew first with the lower jaw incisors, working against a hard dental pad on the front part upper palate, then second with the molars, grinding plant material down further. Chewing stimulates saliva production containing enzymes capable of breaking down fats and starches and helps to buffer the pH levels in the reticulum and rumen segments of the stomach.
2. Esophagus
   When the cattle swallows the plant material and saliva mix, it will travel down the esophagus to the rumen. The esophagus performs the swallowing action through waves of muscle contractions, moving the food down. It has a bidirectional function. Cattle need to regurgitate “cud,” under-chewed plant matter. Once the cow is finished chewing the cud, it again swallows the matter back down to the stomach.
3. Stomach
   There are four sections of the stomach — rumen, reticulum, omasum and abomasum.

*Rumen
The rumen is the first area of the cow’s stomach, connected to the cattle’s esophagus. This compartment acts as storage for chewed vegetation and forms balls of cud. Cud consists of large, non-digestible pieces of plant matter that must be regurgitated, chewed a second time and swallowed before continuing through the process.
The rumen absorbs nutrients through papillae of the rumen wall and facilitates fermentation, creating the rumen bacteria and rumen microbes necessary to break down and digest the proteins in feed. Microorganisms in the rumen are responsible for digesting cellulose and complex starches, as well as synthesizing protein, B vitamins and vitamin K. These microbial communities also produce SCFA’s or VFA’s and ammonia rich in nitrogen which can later be used to produce amino acids and proteins.
Methanogens convert CO2 and H2 to methane
*Reticulum
The reticulum has an inner lining appears with a similar structure to a honeycomb. It is attached to the rumen with only a thin tissue divider. This component holds heavy or dense objects — such as metal pieces and rocks — and trap large feed particles that are not small enough to be digested. The reticulum facilitates regurgitation. Both the rumen and reticulum contain digestive bacteria, so no acid is included in the regurgitation of materials.

*Omasum
The globe-shaped omasum is lined with large leaves and folds of tissue that resemble the pages of a book. These folds absorb water and nutrients from feed that passes through after its second round of chewing.

*Abomasum
The abomasum is the last component of the stomach. This true stomach is the only compartment of the stomach lined with glands. These glands release hydrochloric acid and digestive enzymes to help the abomasum further break down feed and plant material.

4. Small Intestine
   The small intestine has three main sections — the duodenum, jejunum and ileum — that work together to complete most of the actual digestive process. In the duodenum, the section connected to the stomach, secretions from the gallbladder and pancreas mix with the partially digested matter. This process balances the pH in the intestine, ensuring the digestive enzymes work correctly. The jejunum section is lined with small, finger-like projections known as villi, which increase the intestinal surface area and absorb nutrients. The ileum absorbs vitamin B12, bile salts and any nutrients that passed through the jejunum. At the end of the ileum is a valve, preventing any backward flow of materials. Throughout the small intestine, muscular contractions move the matter forward.
5. Cecum
   Sitting between the small and large intestines is a three-foot-long pouch called the cecum. It has little function besides providing storage and a transition between the two intestines, but it does aid in the continual breaking down of material.
6. Large Intestine
   It absorbs remaining water and contains bacteria microbes that finish digestion and produce vitamins the animal needs to grow and remain healthy. Its last job is to eliminate any undigested and unabsorbed food from the system in the form of waste.

Question 17

What is coprophagy?

Answer 17

Eating faeces to uptake the remaining nutrients

Question 18

where is bile produced and where is it transported to?

Answer 18

Bile is produced in the liver and it is then sent down to the gall bladder where it is stored and then its released into the duodenum.

Question 19

What are the 4 colon names?

Answer 19

Ascending colon, transverse colon, descending colon and sigmoid colon

Question 20

What is the structure of the esophagus?

Answer 20

The upper esophageal sphincter (UES) is a bundle of muscles at the top of the esophagus. These have conscious control, used when breathing, eating, belching, and vomiting. They keep food and secretions from going down the windpipe.
Inside layer is circular which squeezes food downwards
Outside layer is longitudinal which moves food along and both of these help segment food and break it down into smaller clumps this process is called peristalsis.

The esophageal wall consists of four layers: a mucosa, a submucosa, a muscularis propria, and an adventitia.

Question 21

How many layers of muscles are there in the stomach lining (serosa is very outer layer)

Answer 21

3 longitudinal, middle circular and inner oblique layer therefore the stomach can contract in all different directions

Question 22

What are hindgut fermenters?

Answer 22

They have a fermentation chamber after the stomach. They also have a large cecum e.g pigs and rabbits