7. GIT - physiology 1

Question 1

What is prehension?

Answer 1

the act of moving food into the mouth, directly controlled by the CNS

Question 2

what nerves are involved in prehension?

Answer 2

• facial nerve
• glossopharyngeal nerve
• the motor branch of the trigeminal nerve

Question 3

what is mastication?

Answer 3

the first act of digestion

Question 4

what does mastication allow?

Answer 4

• breakdown of food particles to increase surface area for digestion
• Moisten and lubricate food to prevent it from getting stuck in the oesophagus

Question 5

what structures are involved in mastication?

Answer 5

• Stratified squamous epithelium
• Terminal branches of sensory neurons

Question 6

what are the 2 types of saliva?

Answer 6

• mucous
• serous

Question 7

what salivary glands produces mucous saliva?

Answer 7

• sublingual
• zygomatic

Question 8

what salivary gland produces serous saliva?

Answer 8

parotid

Question 9

describe mucous saliva compared to serous

Answer 9

• mucous is thicker/more viscous
• serous is watery and contains amylase

Question 9

describe mucous saliva compared to serous

Answer 9

• mucous is thicker/more viscous
• serous is watery and contains amylase

Question 10

what is mucous saliva important for?

Answer 10

binding food into a bolus

Question 11

what are salivary gland mainly regulated by?

Answer 11

parasympathetic nervous system

Question 12

describe the salivary gland structure?

Answer 12

• Striated duct (in and out)
• Intercalated ducts (bunches of grapes)
• Acini (secrete saliva)
• Nerve fibres on the outside of the gland - only controlled by neurons

Question 13

how are salivary glands controlled?

Answer 13

• regulated mainly by the parasympathetic nervous system
• the stimulation of nerve fibres on the end of the acini results in saliva production
• the sympathetic nervous system activates b-adrenergic receptors in salivary secretory cells: occurs in fight or flight and produces a smaller quantity of vicious saliva. stimulation could be carnivores about to attack.

Question 14

list the constituents of saliva including
- function
- component
- how it works

Answer 14

Function: lubrication
Component: Mucins (glycoproteins)
How: mix with water to form mucous

Function: pH regulation
component: HCO3-
How: neutralisation

Function: antibacterial
Component: Lysozyme antibodies
how: keep the amount of bacteria in check 21

Question 15

how are Omnivores, Single-stomached herbivores, and some avians saliva specialised

Answer 15

Starch digestion - amylase in saliva - mixed with food before stomach. Acts in stomach

Question 16

how are young calves saliva specilised

Answer 16

Fat digestion - using lingual lipase to help digest milk

Question 17

how are canines and rodents saliva specialised

Answer 17

thermoregulation:
- Panting in canines
- Rodents lick fur to help with evaporation from the skin

Question 18

how are leaf-eaters saliva specilised

Answer 18

binding of tannins
Tannins bitter and sometimes unpalatable - uses Binding proteins

Question 19

how are animals with forestomachs saliva specilised

Answer 19

Providing urea; Urea diffuses from the blood into saliva

Question 20

how are ruminants saliva specilised

Answer 20

saliva is alkaline, this is necessary for the neutralisation of fermentation products

Question 21

what is the problem with ruminant saliva specialisation

Answer 21

H20 and electrolytes secreted in saliva must be reabsorbed rapidly or else the cow can become dehydrated and become acidotic

Question 22

what is deglutition?

Answer 22

process of swallowing

Question 23

what are the 2 phases of deglutition

Answer 23

• voluntary
• involuntary

Question 24

what happens in the voluntary phase of deglutition?

Answer 24

chewed food is moulded into a bolus and moved to the pharynx (swallowed)

Question 25

what happens in the involuntary phase of deglutition?

Answer 25

1) Breathing stops momentarily 2) Soft palate is elevated 3) The tongue is pressed against the hard palate 4) The glottis is pulled under the epiglottis 5) When all openings into the pharynx are closed a wave of muscular contraction passes over the walls of the pharynx 6) The upper oesophageal sphincter relaxes

Question 26

how is deglutition controlled?

Answer 26

Involuntary - controlled by motor neurons in various centres of the brainstem - Efferent nerve fibres travel in the facial, vagus, hypoglossal and glossopharyngeal nerves

Question 27

list the layers of the oesophagus

Answer 27

Serosa Muscularis layer (longitudinal and circular muscle ) Submucosa layer Mucosa layer (Muscularis mucosae, lamina propria, epithelium)

Question 28

describe the serosa layer of the oesophagus

Answer 28

connective tissue that covers the longitudinal muscle, which is the base layer of the muscularis

Question 29

describe the muscularis layer of the oesophagus

Answer 29

has 2 sublayers: longitudinal and circular muscle. - Longitudinal - runs down the oesophagus from mouth to stomach - Circular muscle - runs around the oesophagus in rings

Question 30

describe the submucosa layer of the oesophagus

Answer 30

all the blood vessels and nerves that supply and stimulate the muscle layers

Question 31

what is the mucosa layer of the oesophagus made up of

Answer 31

Muscularis mucosae Lamina propria Epithelium

Question 32

what is the function of the mucosa layer of the oesophagus

Answer 32

secrete mucus

Question 33

what are the muscle types in the oesophagus

Answer 33

Striated muscle Smooth muscle

Question 34

what is the structure of stratified muscle?

Answer 34

multinucleated layer, made up of myofibres and striations related to sarcomeres

Question 35

what is the structure of smooth muscle?

Answer 35

made of single cells with single nucleus as don’t require as much energy

Question 36

what is striated muscle under control of?

Answer 36

vagus nerve

Question 37

what is smooth muscle under control of?

Answer 37

ENS (enteric nervous system)

Question 38

describe the skeletal Muscular variation in the oesophagus between species

Answer 38

- dogs, cattle and sheep the entire length of the oesophagus is striated - In horses, primates and cats a portion of the oesophagus is smooth muscle

Question 39

what are oesophagus sphincters

Answer 39

bands of muscle which are tightly controlled and constricted when deglutition is not taking place Upper (mouth end) and lower (stomach end) sphincter at each end of oesophagus

Question 40

how is the lower sphincter aided by the anatomical attachment to the stomach?

Answer 40

tight bend in the oesophagus just as it goes towards the stomach and the pressure from this structural link helps keep the sphincter closed. Reflux otherwise.

Question 41

describe how peristalsis occurs/ is carried out

Answer 41

- Comes in primary and secondary waves; primary waves are much stronger, secondary waves much weaker in force - Circular and longitudinal muscles are paired. - Circular muscle contracts while longitudinal muscle is relaxed which pushes the bolus (propulsion), the circular muscle is relaxed and longitudinal contracted where the bolus is