Skin

Question 1

Why is the epidermis impermeable to water

Answer 1

To protect against dehydration

Question 2

In thick skin what is different to thin skin

Answer 2

The number of epithelial cell layers and the thickness of the keratin layer are greater

Question 3

In areas where the cells are exposed to abrasion the surface epithelial layers are covered by a layer of what

Answer 3

Keratin

Question 4

What is keratin

Answer 4

A fibrous proteins synthesised in the cells as they move upwards towards the surface

Question 5

Which layer of the epidermis does cell division occur in

Answer 5

Stratum germinativum/ stratum basale

One daughter cell remains as a stem cell and the other moves and differentiates to become part of the protective barrier

Question 6

Describe the layer of the epidermis which is only present in thick skin

Answer 6

The stratum lucidum

A layer of flattened dead cells, rich in keratin

It is inert and impervious

Question 7

Which layer are spot / punctate desmosomes most obvious in the epidermis

Answer 7

Stratum spinosum

Question 8

What are the granules within the cells of the stratum granulosum known as

What do they contain

Answer 8

Keratohyalin granules

Contain proteins that promote aggregation of keratin fibres eg filaggrin

Question 9

What are the two types of sweat gland and how do both types release their products

Answer 9

Eccrine / merocrine
Apocrine

Via merocrine secretion, which involves exocytosis of secretory vacuoles

Question 10

Discuss eccrine sweat glands

Answer 10

Secrete a watery secretion and Are distributed all over the body

They are simple tubular glands with a coiled secretory part and a straight excretory duct

They extend from the dermis to the skin surface

Question 11

Where Does the coiled secretory part of eccrine sweat glands lie and what epithelium lines it

Answer 11

Lies deep in the dermis

It is lined by one layer of columnar or high cuboidal cells surrounding a central lumen into which the secretion is extruded

Question 12

Describe the straight excretory ducts of eccrine cells

Answer 12

Lined by stratified cuboidal epithelium (usually two layers)

The cells are smaller in diameter and show darker staining than those in a secretory portion

Question 13

What do apocrine do

Answer 13

Secrete a fatty sweat and are usually associated with hair follicles

Question 14

Where are apocrine sweat glands usually found

Answer 14

In humans they are mainly found in the armpits, genital region, areola of the breast, eyelids and in the ear

Question 15

What is the structure of apocrine sweat glands

Answer 15

They are simple coiled tubular glands with a secretory part deep in the dermis and hypodermis

The excretory duct opens into the hair follicle

Question 16

What does sweat contain

Answer 16

Water, electrolytes and waste products

Question 17

What control are eccrine sweat glands under

Answer 17

Sympathetic cholinergic control

Question 18

What do sebaceous glands do

Answer 18

Discharge a fatty sebum into the hair follicles to lubricate growing hairs

Question 19

Describe the arrector pili muscles

Answer 19

They are small bundles of smooth-muscle that attach to the hair follicle at one end and to the dermal connective tissue at the other

Question 20

Where are sebaceous glands found

Answer 20

Throughout the hard skin of all mammals

Question 21

What is sebum

Answer 21

And oily secretion composed of triglycerides, phospholipids, and cholesterol,

Question 22

Describe the structure of a sebaceous gland

Answer 22

Consists of a solid mass of large epithelial secretory cells surrounded by a sheath of connective-tissue

The secretory cells are full of lipid droplets

Question 23

What kind of gland are sebaceous glands

Answer 23

Holocrine glands

Question 24

What does holocrine secretion involve

Answer 24

The discharge of the whole cells, released as a cell fragments, forming sebum

Question 25

Describe the structure of the hair shaft

Answer 25

It consists of an inner core (the medulla), and outer ring (the cortex) and a surface layer (the cuticle)

The cortex and cuticle contain hard keratin, which does not form scales and is more permanent and soft keratin

Question 26

How is hair produced

Answer 26

From a group of cells at the bottom of the follicle

All the layers of the epidermis invaginate to form the top of the cylindrical follicle, but the structure becomes simpler further down until there is only the stratum germinativum that forms the hair

Question 27

What is the Panician corpuscle

Answer 27

A sensory Mccanna receptors are located in the hypodermis

It responds to deep pressure and vibration

Question 28

Describe the structure of the Pacinian corpuscle

Answer 28

Often of large diameter, it consists of a fine capsule enclosing concentric layers of flatten cells that give the appearance of an onion

At the centre of the corpuscle there is a non-myelinated afferent nerves fibre that becomes myelinated as it leaves the corpuscle

Question 29

How big is the diameter of a Panician corpuscle

Answer 29

1-2mm long by 0.5 -1 mm in diameter