Histology of skin

Question 1

Where is the skin thickest?

Answer 1

Soles of the feet and palms of the hands

Question 2

Where is the skin thinnest?

Answer 2

Parts of the abdomens and thorax, lips, eyelids and some parts of external genitalia

Question 3

Is keratinised epithelium dead or alive?

Answer 3

Dead

Question 4

How does keratinised epithelium stain?

Answer 4

Pink

Question 5

What lies just beneath the keratinised epithelium, what how does it stain?

Answer 5

A darkly staining granular layer which synthesise keratin. They contain purple keratohyaline (the precursor to keratin)

Question 6

What are the majority of the cells in the epidermis?

Answer 6

Keratinocytes, which are derived from stem cells within the germinal layer of the epidermis that rests on the basement membrane.

Question 7

What other cells are present in the germinal layer of the epidermis, that is responsible for skin colour?

Answer 7

Melanocytes- produce melanin pigment granules that are transferred to keratinocytes

Question 8

Where is melanin stored within the epidermis?

Answer 8

In keratinocytes

Question 9

What are melanocytes derived from, and where do they migrate to?

Answer 9

The neural crest of the embryo and migrate into the epidermis during development

Question 10

What causes skin colour?

Answer 10

Skin colour is proportional to the amount of melanin stored in keratinocytes. The number of melanocytes doesn’t change with race or skin colour.

Question 11

What is the thickest layer of the epidermis?

Answer 11

The spinous layer- between the lowest most germinal layer and the granular layer

Question 12

Where is the spinous layer of the epidermis found?

Answer 12

Between the lowest most germinal layer and the granular layer near the surface.

Question 13

What is the function of the spinous layer of epidermis?

Answer 13

It’s cells are held together by desmosomes (intermediate filaments) that prevent the skin from splitting when stretched

Question 14

Where are Langerhan’s cells present and where are they easiest to see?

Answer 14

In the epidermis and most easily seen in the spinous (prickle) layer

Question 15

What do Langerhans cells look like?

Answer 15

They have a pale cytoplasm and an irregular (ovoid) shapes nucleus

Question 16

What is the function of Langerhans cells?

Answer 16

They are antigen detecting cells, important in the immune system and increase in number during inflammatory situations

Question 17

Where are Merkel cells found?

Answer 17

In the basal layer of the epidermis

Question 18

What is the function of Merkel cells?

Answer 18

They form synapses with nerve cells in the dermis and convey the sensation of fine touch

Question 19

What is the origin of hair follicles?

Answer 19

Although the roots of hair project into the dermis of the skin, they are epidermal in origin

Question 20

Where to hairs arise from?

Answer 20

The germinative layer of the epithelium within the hair bulb

Question 21

Where do hairs get their colour from?

Answer 21

Melanocytes produce melanin and are present in the hair bulb in the germinative layer

Question 22

What is the hair surrounded by?

Answer 22

A collagenous (type 1) follicle sheath

Question 23

What allows the hairs to stand on end?

Answer 23

An erector pilli muscle (smooth muscle) inserted into the follicle sheath and is autonomically innervated

Question 24

What lubricates hair?

Answer 24

Sebaceous glands which open into the shaft that the hair follicle takes through the dermis and epidermis and secrete sebum

Question 25

What are nails composed of?

Answer 25

Compacted keratin

Question 26

Where do nails arise from?

Answer 26

A nail matrix they are located under the cuticle at the proximal end of the nail

Question 27

What is the dermis composed of?

Answer 27

Two layers of connective tissue: The outer layer closest to the epidermis is fibrous and composed of collagen and elastin The inner layer contains much adipose tissue

Question 28

What structures are embedded in the dermis?

Answer 28

Roots of hairs, glands, blood vessels and nerves

Question 29

What are the most common form of sweat gland?

Answer 29

Eccrine (apocrine are less common and mainly found in the armpits, anus and the external genitalia)

Question 30

Describe eccrine glands

Answer 30

They are tightly coiled fluid secreting cells surrounded by myoepithelial cells which help to expel sweat. These are accompanied by a straight duct lined by simple cuboidal epithelium, which extend to the surface of the skin

Question 31

What are the two main sensory transducers within the dermis of the skin?

Answer 31

The pacinian corpuscle (resembles a section through an onion) The Meissner’s corpuscle (numerous and have a spiral appearance)

Question 32

What are the eyelids covered by?

Answer 32

A thin layer of hairy skin and a row of prominent eye lashes

Question 33

What is the inside of the eye lid lined by?

Answer 33

A moist conjunctiva consisting of stratified columnar epithelium (just two layers)

Question 34

What is the substance of the eyelid composed of?

Answer 34

A single row of eyelashes Striated muscle fibres of the orbicularis occult muscle Glands (largest being the meibomian gland)

Question 35

Describe the nipple

Answer 35

A raised area of skin with a fibro- muscular core containing 12-20 small opening of lactiferous (milk) ducts

Question 36

Describe the areola

Answer 36

Surroundes the nipple, normally hairless but contains many sebaceous glands

Question 37

What happens to the ducts of the breasts at pregnancy?

Answer 37

They develop terminal secretory alveoli, which contain secretory cells that produce milk proteins (apocrine secretion), milk fats (merocrine secretion) and an ion rich watery solution

Question 38

What do apocrine sweat glands look like?

Answer 38

Very pink staining

Question 39

What does the pascinian corpuscle detect?

Answer 39

Pressure

Question 40

What is the pacinian corpuscle made up of?

Answer 40

Schwann cells around a nerve

Question 41

What do meissners corpuscle detect?

Answer 41

Light touch

Question 42

Name the 5 layers of the epidermis?

Answer 42

1. Stratum basale- has stem cells for keratinocytes and contains melanocytes 2. Stratum spinosum (pickle layer)- contains desmosomes 3. Stratum granulum- where keratinocytes stay 4. Stratum lucidum- only found on palms, fingertips and soles of feet 5. Stratum corneum- keratinised layer

Question 43

What are the layers of the skin called?

Answer 43

Epidermis- outer layer Subcutaneous layer Dermis Extraepidermal parts- where epidermis goes into dermis (hair bulbs)