Digestive system

Question 1

The four digestive processes explained

Answer 1

Ingestion – The process of taking food into the body.

Digestion – The process of breaking down food into its component parts in the stomach and small intestine.

Absorption – Occurs in the small intestine and large intestine – the process of transferring nutrients from the intestine into the bloodstream.

Excretion – Removal of indigestible material as faeces.

Question 2

Order of the digestive tract

Answer 2

Oral Cavity
Oropharynx
Oesophagus
Stomach
Duodenum
Jejunum
Ileum
Caecum
Colon
Rectum
Anus

Question 2

Name the four accessory digestive structures

Answer 2

Salivary Glands,
Liver,
Gall Bladder,
Pancreas

Question 3

Describe four functions of the oral cavity

Answer 3

• Picking up food with the lips and tongue.
• Chewing to break up food into smaller boluses to aid swallowing.
• Lubrication of food with mucus and saliva.
• Digestion of carbohydrates in the mouth by salivary amylase (omnivores and herbivores only).

Question 4

six functions of the tongue

Answer 4

• To aid ingestion
• To carry receptors for taste
• To form a bolus from food for swallowing
• Grooming
• Thermoregulation – flattening of the tongue and increased blood supply to the capillaries of the tongue allows saliva to evaporate and cooling of the body.
• Vocalisation – complex movements of the tongue allow an animal to vocalise.

Question 5

The tongue is made of (1) allowing complex voluntary movement, with its root attached to the (2)

Answer 5

Striated muscle
Hyoid bone

Question 6

the membrane which covers the gums is known as

Answer 6

the gingival membrane

Question 7

incisor shape and function

Answer 7

small, chisel shaped with single root
Used for nibbling, cutting and grooming

Question 8

Canine shape and function

Answer 8

pointed, curved, single root
grasping, gripping and piercing prey

Question 9

Molar and pre molar

Answer 9

premolar<3>molar roots
Flatter surface with cusps
Shearing flesh with cusps,
flattened surfaces used for crushing and grinding.

Question 10

saliva - structure and source

Answer 10

consists of 99:1 water:mucus
produced in salivary glands

Question 11

function of soft palate

Answer 11

divide the naso/oro-pharynx

Question 12

What system is the tonsil part of and what is its function

Answer 12

lymphatic system - protects the animal from disease

Question 13

five steps of swallowing

Answer 13

• Food is rolled into a bolus by the tongue and is passed to the back of the mouth.
• The muscles of the pharynx contract, pushing the food bolus to the osophagus
• The epiglottis closes, preventing food entering the larynx.
• A wave of peristalsis pushes food down the osophagus.
• The epiglottis opens allowing respiration to begin again.

Question 14

Function and location of esophagus

Answer 14

The osophagus carries food from the pharynx to the stomach. It lies dorsal and slightly to the left of the trachea. As it passes through the thorax it runs through the mediastinum, dorsal to the heart and between the lungs.

Question 15

oesophogus structure

Answer 15

The osophagus is a tubular structure containing longitudinal and circular bands of smooth muscle. It is lined by stratified squamous epithelium.

Question 16

structure and location of stomach within body

Answer 16

The stomach is a c-shaped sac-like organ which lies on the left side of the abdomen. it lies caudal to the diaphragm and cranial to the liver

Question 17

stucture of stomach wall (4)

Answer 17

The stomach wall is lined by mucosa and has deep folds called rugae.

Within the wall are gastric pits containing:
- Goblet cells which produce mucus to protect the stomach wall from acid and digestive enzymes

• Chief cells which produce pepsinogen.
• Parietal cells which produce gastric (hydrochloric) acid.

Question 18

three main functions of stomach

Answer 18

• To act as a reservoir for foods.
• To break up food and mix it with gastric juices
• To begin protein digestion

Question 19

which movements take place within the stomach and their purpose

Answer 19

• Peristalsis – to propel food material through the stomach
• Rhythmic segmentation – to break up and mix food boluses.

Question 20

processes which occur in the small intestine

Answer 20

digestion and absorbtion

Question 21

The stomach breaks food down to a substance known as

Answer 21

Chyme

Question 22

Small intestine consists of 3 parts;

Answer 22

Duodenum, Jejunum and Ileum

Question 23

which structures empty into the first part of the small intestine

Answer 23

the pancreatic duct and the common bile duct

Question 24

Describe parts of the ileocaecocolic junction

Answer 24

The ileocaecocolic (or ileocaecal) junction, at which location the ileum, caecum and colon meet.

Question 25

25. What is the function of the villi in the wall of the small intestine?

Answer 25

To improve efficiency of digestion and absorption of the nutrients from the small intestine by increasing the surface area.

Question 26

properties of intestinal villi which aid with absorption

Answer 26

- Large Surface Area - Excellent blood supply from a network of internal capillaries - They have a thin layer of cells lining their wall - Surface area is further increased by the presence of microvilli on the surface of the epithelial cells lining the villi.

Question 27

Which two structures are located within the villi to transports absorbed substances

Answer 27

- Capillary Network – absorb carbohydrates and proteins to relay them to the hepatic portal vein - Lacteal – to absorb fat in the form of chyle (the product of fat digestion) and relay it to the lymphatic system (specifically to the cisterna chyli).

Question 28

29. Name and describe (in terms of function) the four structures which make up the large intestine

Answer 28

- Caecum – a short blind ending tube. This is used for bacterial fermentation in hind-gut fermenting herbivores but has no significance in carnivores. - Colon – made up of the ascending, transverse and descending. Water, vitamins and electrolytes are absorbed here. - Rectum – found within the pelvic cavity, stores faeces before release. - Anal Sphincter – controls the passage of faeces out of the body.

Question 29

eight functions of liver

Answer 29

- Metabolism of carbohydrates and storage of glycogen - Metabolism of proteins – including manufacture of plasma proteins, regulation of amino acids and production of urea from surplus amino acids. - Metabolism of fat - Bile formation which is subsequently stored in the gall bladder - Destruction of old red blood cells - Formation of new red blood cells - Storage of vitamins (mainly fat soluble ones) - Storage of iron - Production of heat for the body - Detoxification

Question 30

where is the pancreas located

Answer 30

within the 'U' of the duodenum

Question 31

function of bicarbonate

Answer 31

To neutralise the acid found in chyme.

Question 32

function of trypsinogen

Answer 32

A precursor to trypsin which is activated in the small intestine.

Question 33

function of typsin

Answer 33

Breaks down proteins and peptides into amino acids

Question 34

function of lipase

Answer 34

converts fats into fatty acids and glycerol

Question 35

function of amylase

Answer 35

breaks down starch into maltose

Question 36

explain the process of trypsin

Answer 36

Active trypsin is not normally present in the pancreas, instead, the enzyme precursor trypsinogen is found in the pancreas. Activation of trypsinogen to trypsin is prevented in the pancreas by a trypsin inhibitor. Trypsin becomes activated once it reaches its destination; the small intestine

Question 37

where is bile made and stored

Answer 37

made in the liver and stored in gall bladder

Question 38

function of bile

Answer 38

emulsify fat globules (to increase surface area for lipase to act)

Question 39

function of mucus

Answer 39

Lubricates food and protects the stomach wall from auto-digestion.

Question 40

function of hydrochloric acid

Answer 40

Begins the breakdown of proteins and creates a low pH to facilitate digestion

Question 41

function of pepsinogen

Answer 41

A precursor to pepsin which is not active so prevents damage to the stomach wall, where it is produced

Question 42

pepsin function

Answer 42

Breaks down proteins into peptides (is activated from pepsinogen in the acidic environment of the stomach).