Integumentary System

Question 1

What are the three layers of skin called? What order from top to bottom are they in?

Answer 1

1) Epidermis, 2) Dermis, 3) Hypodermis

Question 2

What is the Epidermis?

Answer 2

The top layer of skin, composed of layers of cells, with dividing cells in the lower layers. Top cells are dead with a lot of keratin in them and fall off. Cells deeper in the Epidermis don’t keratinise but can produce melanin.

Question 3

What is the Dermis?

Answer 3

The second layer of skin, which contains collagen and elastic protein fibres which give skin its strength and elasticity.

Question 4

What is the Hypodermis?

Answer 4

Attaches the skin to the underlying structures. It consists of fat or adipose tissue.

Question 5

What is Keratin?

Answer 5

It is a tough, fibrous protein which is resistant and waterproof.

Question 6

What does Keratin form?

Answer 6

Hair, feathers, scales, nails, claws, hooves and the outer layer of horns and the outermost layer of skin.

Question 7

What gives skin pigmentation?

Answer 7

Melanin. Melanin producing cells are called melanocytes.

Question 8

What does the Dermis contain?

Answer 8

At various levels, it contains hair follicles, sweat and sebaceous glands, blood vessels and capillaries, nerves and nerves endings (pain, pressure and temperature).

Question 9

Why don’t tattoos slough off with dead skin cells?

Answer 9

Tattoo ink is injected into the dermis layer of the skin, which doesn’t slough off.

Question 10

What is mitosis?

Answer 10

Mitosis of a parent cell produces two daughter cells that are identical to both the parent cell and each other. A chromosome from the parent cell is replicated and a copy of each chromosome goes to each of the daughter cells.

Question 11

What are the functions of the skin?

Answer 11

Protection, temperature regulation, stimulus reception and vitamin production.

Question 12

What does the skin protect from?

Answer 12

Minor knocks and bumps, UV rays, microbes, heat loss and water loss.

Question 13

How does the skin regulate temperature?

Answer 13

Sweating cools the skin, pilo-erection, receptors for temperature, fat, vasodilation or vasoconstriction.

Question 14

What stimuli does the skin have receptors for?

Answer 14

Touch, pressure, pain, hot and cold.

Question 15

What are some waste products removed by the skin?

Answer 15

Water and salts.

Question 16

What role does skin have in sexual attraction?

Answer 16

Pheromones and colouration can attract mates.

Question 17

What vitamin is produced in the skin? What is its use in the body?

Answer 17

Vitamin D. It is used to build healthy bones.

Question 18

What is the hypodermis also called?

Answer 18

The subcutaneous layer.

Question 19

What is mitosis used for?

Answer 19

Growth, repair and body maintenance.

Question 20

What are calluses and footpads made of?

Answer 20

Thickenings or swellings of the outermost, keratinised layers of the epidermis. Usually present on surfaces subject to wear.

Question 21

What is a claw? What is the difference between a nail and a claw?

Answer 21

It forms a protection for the top, sides and tip of a terminal toe joint. Beneath the claw there is a growing layer, protected on its base by a fold of skin, from which the claw continually grows outwards. On the under surface is a pad of softer, less keranised tissue, a subunguis, which effects a transition between the claw and the epidermis. A nail is a broadened and flattened claw restricted to the upper surface of the finger or toe.

Question 22

What is a hoof made of?

Answer 22

It is a shorted and broadened shealth of keratinised material that surrounds the toe tip. It is characteristic of ungulate mammals.

Question 23

What are horns?

Answer 23

The core of a horn is a spike of bone arising in the dermis and fused with the skull. Sheathing and extending this is a hollow cone of true horn substance, formed by kerantinisation of skin epidermis. Neither core nor sheath is ever shed, and these typical horns, variously curved, are never branched.

Question 24

What are antlers?

Answer 24

The antlers usually consist solely of bone. During growth it is covered by skin in the form of velvet. An antler is shed annually and tends to be branched, increasingly so in older animals.

Question 25

What is a contour feather?

Answer 25

Large feathers which sheath the body surface and includes feathers of the wing and tail.

Question 26

What makes a mature feather?

Answer 26

It’s formed entirely from modified and keratinised epithelial (outer layer) cells. The continuity of the feather surface is maintained by a complicated system of barbules, each one interlocks with another nearby.

Question 27

How can disrupted barbules be repaired?

Answer 27

By a bird preening.

Question 28

What is a down feather?

Answer 28

They make the entire body covering for a chick and underline contour feathers over most of the body of the adult bird. These form the main insulation.

Question 29

Where is the oil birds use when grooming secreted from? What does this oil do?

Answer 29

Oil is secreted by the preen/uropygial glands, near the base of the tail. This oil waterproofs the feathers.

Question 30

What are the functions of grooming in birds?

Answer 30

Cleaning, removing ectoparasites and distributing oil.

Question 31

Where is hair formed from? What is associated with each hair folicle? What do these do?

Answer 31

Keranitised epidermis that extends down into the dermis. Each hair follicle is associated with hair erector/arrector pili muscle and a sebaceous gland. The hair erector muscle causes hair to move up or stand up. The sebaceous gland secretes sebum to lubricate and waterproof hairs, it also produces a smell that acts as a territorial marker.

Question 32

What is the function of pilo-erection?

Answer 32

In thickly furred animals, rising and depressing hairs can bring changes in insolation. It can also stand up and make the animal appear larger, which helps with aggressive or defensive behaviour.

Question 33

What is hair used for?

Answer 33

It is mainly used for insolating and thermal regulation, it can also provide colour markings which can be used for defence and for recognition.

Question 34

What are the types of hairs?

Answer 34

Guard hairs, wool hairs and vibrissae or tactile hairs.

Question 35

What are guard hairs?

Answer 35

They are long hairs that provide the topcoat, they provide the waterproof layer of the topcoat. Only one hair grows per follicle.

Question 36

What are wool hairs?

Answer 36

They provide the undercoat, providing an insulating underlayer to the topcoat. They are shorter, softer hairs that trap air in-between them and keep the body warm. They make up the main part of the puppy coat and multiple even many wool hairs can grow per follicle.

Question 37

What are tactile hairs?

Answer 37

They are also known as vibrissae. They are thicker than guard hairs and project beyond the rest of the coat. They grow from specialised follicles that project deep into the hypodermis. They have nerve endings at their base that respond to movement of the hair.

Question 38

Where are the most tactile hairs found?

Answer 38

Most of them are found around the head, on the upper lip and above the eyes. Dogs can have a substantial tuft of them on the check and cats can have a tuft of them on their carpus.

Question 39

What is moulting?

Answer 39

Seasonal shedding of hair.

Question 40

How often do dogs and cats most commonly moult?

Answer 40

Most dogs shed during spring and autumn. Cats can shed most heavily in spring. However many household pets shed all year round due to the effect of household living such as central heating and electricity.