Organs Of The Gut

Question 1

Each organ of the gut is specialised (adapted) for a particular function

Answer 1

…

Question 2

Mouth

Answer 2

-As food enters the mouth it is mixed with saliva and chewed
-Saliva is watery and alkaline containing mucus and as an enzyme salivary amylase
- salivary amylase begins starch digestion in the mouth
- the mucus binds food together into a sooth, round bolus that can be easily swallowed
- saliva contains substances such as lysozyme and antibodies which inhibit bacteria
The mouth contains many species of bacteria

Question 3

Saliva

Answer 3

• The alkali and electrolytes in saliva help to protect tooth enamel by maintaining the chemical balance
• there is a particular high concentration of calcium in saliva - why?
• saliva dissolves food molecules so that they can be tasted by taste buds on the tongue
• saliva 1/2 litres secreted each day. Most is swallowed and absorbed
• food in mouth stimulates saliva

Question 4

Oropharynx

Answer 4

-Funnel shaped tube containing skeletal muscle
-Has a respiratory and digestive function
- swallowing - muscular contractions propel food into the oesophagus and then into the stomach
- because both food and air pass through the pharynx. A flap of connective tissue called epiglottis closes of over the trachea when food is swallowed to prevent chocking
The pharynx is also important in vocalisation

Question 5

The oesophagus

Answer 5

• a tube of approx 10 ins which runs behind the trachea from the pharynx, through the mediastinum between the lungs and curving slightly upwards before entering the stomach
• there is an upper and a lower oesophageal sphincter (where the musclaris becomes slightly more prominent)

Functions-

• to produce mucus to lubricator the bolus of food
• involuntary muscle layer propels food into stomach
• no chemical actions or enzymes

Question 6

Stomach

Answer 6

• The stomach is a temporary storage tank for food as well as initiating some protein digestion
• the three layers of muscle allow the stomach to mix, churn and pummel food physically breaking it down into semi liquid state (chyme)
• the mucosa of the stomach is an epithelium composed almost entirely of mucus secreting cells that produce a protective layer of bicarbonate rich alkaline mucus
• this clings to the stomach mucosa and prevents the stomach wall from being damaged by acid and digested enzymes
• food remains in the stomach for 3-4 hours until semi liquid form (chime)
• chyme is delivered into the duodenum at a carefully controlled rate to allow SI to process it and to reduce risk of duodenal ulcers

Question 7

Stomach

Answer 7

-The stomach longing is dotted with millions of deep gastric pits which lead to gastric glands
- these secrete gastric juice which contains:
Pepsinogen
Hydrochloric acid
intrindicfactor
Gastroferrin
Mucus
Pepsinogen in an inactive form of pepsin in protease enzyme
Hydrochloride acuf activate pepsinogen by cleaving it into pepsin

Question 8

Small intestine

Answer 8

-The small intestine is the body’s major digestive organ
-it is a muscular tube, extending from the pyloric sphincter of the large intestine
- food spends on average 3 to 6 hours in the small intestine
- average length 2.5 to 7 m
It has 3 subdivisions:
Dunodenum 5% of the length
Jejunum 35% length
Ileum 60% length

Question 9

Duodenum and accessory glands

Answer 9

• The duodenum received semi liquid chyme from the stomach
• receives pancreatic juice from the pancreas via the pancreatic ducts
• pancreatic juice is a rich mixture of digestive enzymes and alkali
• bile (formed by the liver) also enters the duodenum at the same point, from the gall bladder via the bile duct