Rat dissection 1: external features, alimentary canal and associated vasculature

Question 1

Laboratory rat

Answer 1

Rattus norvegicus

Question 2

Aboral

Answer 2

The end opposite the mouth

Question 3

Oral

Answer 3

The end containing the mouth

Question 4

Anterior

Answer 4

The head end:

Usually the end of a thinner animal that meets the environment

Question 5

Posterior

Answer 5

The tail end

Question 6

Caudal

Answer 6

Toward the tail

Question 7

Cephalic

Answer 7

Toward the head

Question 8

Distal

Answer 8

Away from the point of attachment of a structure on the body
(E.g the toes are distal to the knee)

Question 9

Dorsal

Answer 9

The back of an animal, usually the upper surface, synonymous with posterior for animals that walk upright

Question 10

Ventral

Answer 10

The belly of an animal, usually the lower surface, synonymous with anterior for animals that walk upright

Question 11

Inferior

Answer 11

Below a point of reference

E.g. the mouth is inferior to the nose in humans

Question 12

Superior

Answer 12

Above a point of reference

E.g. the head is superior to the neck

Question 13

Lateral

Answer 13

Away from the plane that divides a bilateral animal into mirror images

Question 14

Medial (median)

Answer 14

On or near to the plane that divides a bilateral animal into mirror images

Question 15

What is the buccal cavity

Answer 15

The area inside the mouth bound

• anteriorly & laterally by the lips and cheeks
• posteriorly and medially by the teeth and/or gums
• also know. As the oral vestibule

Question 16

Which two cavities are separated by the roof of the mouth?

Answer 16

Oral cavity separated from nasal cavity

Question 17

Dental formula of rat

Answer 17

1 0 0 3

Question 18

Dental formula for human

Answer 18

2 1 2 3

Question 19

Deductions from dental formula of rat

Answer 19

• large incisors made from hard enamel = teeth are for biting hard substances such as vegetables and seeds
• molars at back of mouth = chewing
• no canines or premolars, thus not designed to tear or chew meat
• designed for herbivorous environment

Question 20

Deductions from dental formula of human

Answer 20

• Humans have incisors and molars = nite and chew harder foods - vegetables
• humans adapted for omnivorous diet

Question 21

Which system do the lymph nodes belong to

Answer 21

The lymphatic system

Question 22

Function of lymph nodes

Answer 22

• Form part of the immune response

- filter blood and create lymphocytes which attack pathogens in our blood

Question 23

What is the function of the Harderian gland?

Answer 23

• photo protective organ
• locomotion of immune response
• source of thermoregulatory lipids
• source of pheromones
• site of osmoregulation
• lubricant of eye and nictitating membrane (third eyelid)

Question 24

Function of the pectoralis membrane

Answer 24

Enables the movement of the arms towards the body

Question 25

Do rats have a gall bladder? | Explain.

Answer 25

No Rats do not have a gall bladder as they do not need to store bile - bile is secreted directly from the liver into the small intestine via the hepatic bile duct

Question 26

Function of cardiac region of stomach

Answer 26

Prevents reflux back up to the oesophagus

Question 27

Function of pyloric region of the stomach

Answer 27

(Specifically pyloric sphincter) | Prevents food from exiting stomach until lit has been sufficiently digested and broken down

Question 28

Function of the caecum

Answer 28

- absorbs water & salts from undigested foods after intestinal digestion - mixes it with mucus for lubrication

Question 29

Why don’t humans have a caecum?

Answer 29

- in herbivores: caecum stores food material where bacteria are able to break down the cellulose - function no longer occurs in human caecum - (in humans) deadened pouch forming part of the large intestine

Question 30

What is the function of the spleen and to which organ system does it belong?

Answer 30

- filters bloods - aids in homeostasis of bodily fluids - aids in immune system - forms part of lymphatic system in the body

Question 31

What does it mean if a vessel is unpaired?

Answer 31

The vessel does not have a matching branch

Question 32

What is the function of the hepatic portal vein

Answer 32

- carries deoxygenated blood from digestive organs and spleen to liver

Question 33

Function of mouth

Answer 33

- site of ingestion | - where saliva and teeth break down food

Question 34

Oesophagus

Answer 34

- pathway of boils between mouth and stomach | - movement through peristalsis

Question 35

Liver

Answer 35

- Provides bile | - used to emulsify fats

Question 36

Stomach

Answer 36

- chemically and mechanically breaks down the bolus further

Question 37

Gallbladder

Answer 37

Bile storage

Question 38

Pancreas

Answer 38

Secretes pancreatic juices

Question 39

Large intestine

Answer 39

Pathway for chyme to allow for absorption of water from chyme

Question 40

Small intestine

Answer 40

Absorption of nutrients

Question 41

Appendix

Answer 41

Storage of good/ ‘helpful’ bacteria

Question 42

Rectum

Answer 42

Intermediate storage of feces

Question 43

Anus

Answer 43

Region through which feces exit the body