Integumentary System: Embryology, Histology & Hair

Question 1

Where does the epidermis originate from?

Answer 1

Ectoderm

Question 2

What does the dermis originate from?

Answer 2

Mesoderm

Question 3

Where do sweat glands, sebaceous glands and hair follicles originate from?

Answer 3

Mesenchyme (which itself originates from mesoderm)

Question 4

What does ‘thickness of skin’ depend on?

Answer 4

Thickness of epidermis

Question 5

What are the 5 layers of the epidermis? (CLGSB)

Answer 5

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

Question 6

What does the stratum corneum consist of?

Answer 6

Dead epithelial cells that are constantly sloughed off

Question 7

What does the stratum lucidum consist of?

Answer 7

Dead, keratinised epithelial cells with no nucleus

Question 8

What do stratum granulosum epithelial cells consist of?

Answer 8

Multiple layers of keratinised cells and keratohyaline granules

Question 9

What does the stratum spinosum consist of?

Answer 9

Keratinocytes bound by desmosomes

Cytoplasm containing tonofilament

Question 10

What does the stratum basale layer consist of?

Answer 10

Single layer of cuboidal cells

Stem cells which divide to become keratinocytes

Question 11

What cells are found in the epidermis?

Answer 11

Merkel cells - free nerve endings. In basal layer
Keratinocytes - main type of cell
Melanocytes - between basal cites
Langerhans cells - for immunisation

Question 12

What processes take place in the epidermis?

Answer 12

Squamous cells in stratum corneum sloughed off
Migration, differentiation and keratinisation of keratinocytes
Proliferation of keratinocytes on basal layer

Question 13

What is the dermis composed of?

Answer 13

Loose, irregular connective tissue
Vessels and nerves
Hair follicles

Question 14

What are the two layers of the dermis and how do they differ?

Answer 14

Reticulum layer - loose connective tissue

Papillary layer - dense connective tissue, contains glands & hair follicles

Question 15

How is blood supplied to the dermis?

Answer 15

Vessels

Arteriovenous anastomoses

Question 16

How is blood supplied to the epidermis?

Answer 16

Diffusion from blood vessels in dermis

Question 17

What are the functions of hairs?

Answer 17

Mechanical protection
Sensory perception
Thermoregulation

Question 18

What are the 3 main parts of a hair?

Answer 18

Shaft - 3 parts
Root - Similar structure to shaft
Bulb - mass at base of root

Question 19

What are the 3 parts of the shaft of a hair? What makes up these layers?

Answer 19

Outer cuticle - single layer of keratinised cells
Cortex - compact dead layer
Medulla - cuboidal cells

Question 20

What epithelium covers the bulb of a hair root?

Answer 20

Stratified squamous epithelium

Question 21

What is the indent found in the bulb of a hair called?

Answer 21

Papilla

Question 22

What is the life cycle of a hair?

Answer 22

Anagen (growth)
Cartagen (regressive, atrophy)
Telegenic (rest)
Repeats

Question 23

What is secreted directly into the hair follicle to protect the hair?

Answer 23

Sebum

Question 24

What are the 3 types of hair follicle?

Answer 24

Tactile - for tactile sense, innervated e.g. whiskers
Single follicles - group together in clusters of 2-4 (pigs)
Compound follicles - multiple hairs coming out of each follicle e.g. cat/dog

Question 25

What is hyperkeratosis?

Answer 25

The thickening of the stratum cornea
Due to excessive keratin levels
On footpads/nose

Question 26

What structures are composed of cornified epidermis?

Answer 26

Hooves, claws, beaks, shells, scales

Question 27

What is the difference between 1st, 2nd and 3rd degree burns?

Answer 27

1st - damage just to epidermis
2nd - damage to epidermis and dermis
3rd degree - damage to epidermis, dermis and subcutaneous layer/hyperdermis