Integumentary System

Question 1

Surface area of skin

Answer 1

1-2m squared

Question 2

2 layers of skin

Answer 2

Epidermis and Dermis

Question 3

What is the epidermis

Answer 3

outermost layer of the skin. It is formed by keratinised stratified squamous epithelium. There are 5 layers which vary in thickness over the body with the thickest parts on the fingers and soles. The epidermis is non-vascular and the nutrients reach the different layers by diffusion.

Question 4

5 layers of epidermis

Answer 4

• stratum corneum – the outermost layer is 30 cells thick, the squamous cells are dead but still tough and provide a waterproof barrier, millions of dead cells are rubbed off daily
• stratum lucidum – lots of keratin (in thick skin only), it is a clear layer
• stratum granulosum – this waterproof layer (3-5 cells thick) has keratinocytes and although this is a tough layer it is also the layer where cells start to degenerate
• stratum spinosum – this layer is several layers thick and gives strength and flexibility to the skin, keratinocytes, Langerhans cells and melanocytes with melanin are found in this layer
• stratum basale – the deepest layer is made up of a single layer of stem cells where mitosis occurs, cell differentiation also starts here, it takes 35 days for cells to move from the stratum basale to the stratum to the corneum, 10% of the skin is replaced daily

Question 5

What is the Stratum Corneum

Answer 5

the outermost layer is 30 cells thick, the squamous cells are dead but still tough and provide a waterproof barrier, millions of dead cells are rubbed off daily

Question 6

What is the Stratum lucidum

Answer 6

lots of keratin (in thick skin only), it is a clear layer

Question 7

What is the stratum granulosum

Answer 7

this waterproof layer (3-5 cells thick) has keratinocytes and although this is a tough layer it is also the layer where cells start to degenerate

Question 8

What is the stratum spinosum

Answer 8

this layer is several layers thick and gives strength and flexibility to the skin, keratinocytes, Langerhans cells and melanocytes with melanin are found in this layer

Question 9

What is the stratum basale

Answer 9

the deepest layer is made up of a single layer of stem cells where mitosis occurs, cell differentiation also starts here, it takes 35 days for cells to move from the stratum basale to the stratum to the corneum, 10% of the skin is replaced daily

Question 10

4 types of epidermal cells in the layers

Answer 10

• keratinocytes – form the barrier, layers of fibrous tissue, most common type of cell, replaced every 35 days
• melanocytes – protection from UV light, give the skin color, contains the pigment melanin
• dendritic or Langerhans cells – part of the immune system, phagocytose foreign substances
• nerve (tactile) cells eg Merkel cells – sensation of touch

Question 11

What is the dermis

Answer 11

makes up the bulk of the skin. It consists of fibrous connective tissue which is tough yet flexible. The dermis has blood vessels, nerve endings, and lymph vessels.

Question 12

What is the papillary layer

Answer 12

lies directly under the epidermis. It is in folds and is responsible for the fingerprints. This layer is made up of areolar connective tissue and also contains pain receptors. It is irregular with folds or ridges which help the gripping ability of the hands and feet. The patter of the ridge is determined by our DNA. Sweat gland pores open along these ridges so where the skin on our fingertips touched a surface it leaves a unique pattern of sweat the mirrors the ridges, these are our fingerprints.

Question 13

What is the reticular layer

Answer 13

is made up of irregular connective tissue containing blood vessels, nerve endings, hair follicles, and glands. This layer accounts for about 80% of the dermis.

Question 14

What is the hyperdermis

Answer 14

subcutaneous tissue or superficial fascia is not really part of the skin. It is closely associated with the skin as it lies directly under the dermis. The subcutaneous tissue is made up of adipose and areolar connective tissue. It stores fat, anchors the skin, and protects and cushions the underlying structures.

Question 15

exocrine glands

Answer 15

maintain body homeostasis. The glands are divided into sudoriferous (sweat) glands and sebaceous (oil) glands.

Question 16

eccrine sweat glands

Answer 16

The glands are simple, coiled ducts with pores that open onto the skin. The watery (sweat) secretions are a hypotonic filtrate from the blood capillaries in the skin and this makes them merocrine glands.

Question 17

What is sweat made up of

Answer 17

99% water with sodium chloride, vitamin C, antibodies, metabolic wastes, and lactic acid. The pH is between 4 and 6.

Question 18

What is sweating

Answer 18

controlled by the autonomic nervous system and thus we have no control over it. Heat-induced sweating helps to control the body temperature. Emotionally induced sweating is brought on by fright or nervousness.

Question 19

apocrine sweat gland

Answer 19

located in the axilla and ano-rectal areas. They are bigger than the eccrine glands and are positioned deep in the dermis and empty into the hair follicles. The secretions are thick and yellow - true sweat plus fats + proteins.

Question 20

What are the two specialised glands

Answer 20

The ceruminous glands are found in the lining of the external ear canal. They produce cerumen (ear wax) which helps to deter insects and block entry to foreign material.
The mammary glands make up the glandular tissue in the breasts. They secrete milk during breastfeeding.

Question 21

sebaceous or oil glands

Answer 21

simple glands which open into the hair follicle. They are found all over the body except on the palms and soles. The cells in these alveolar glands accumulate lipids and then the cells rupture.

Question 22

shaft of the hair

Answer 22

which is a flexible strand of dead, keratinized cells which project from the skin surface. The shaft has are 3 layers – the medulla filled with large cells and air, the cortex with the pigmented cells, and the cuticle which is the keratinized layer which looks like roof tiles.

Question 23

Root

Answer 23

embedded in the skin and is attached to the hair papilla where mitosis takes place.

Question 24

Follicles

Answer 24

composed of epidermal cells and are made up of the bulb which is innervated and thus the hairs are sensitive to touch

Question 25

papilla

Answer 25

protrudes into the bulb which has the blood supply to allow mitosis to take place.

Question 26

Nails

Answer 26

scale-like modification of the epidermis. They are made up of a nail bed with keratinised cells and the site of mitosis. Each nail has a free edge, the body of the nail which is the visible part and the root which is embedded in the skin. The lunula is the white crescent in the nail bed and the nail folds or cuticles are skin overlapping the nails.

Question 27

7 functions of the skin

Answer 27

1. Regulation of body temperature. The body makes about 500 ml of sweat every day. This helps to cool the body. The vasodilation and vasoconstriction of the blood vessels in the skin help to release or conserve heat. The muscle contraction of the arrector muscles during shivering generates heat. Lastly, the subcutaneous fat helps to insulate the body and conserve heat.
2. Protective layer. The skin provides a barrier between the inside, and outside, of the body. The physical barrier is created by tight junctions between the cells and the keratin inside the cells of the epidermis. The biological barriers consist of macrophages, and lysozymes in the oily secretions. The chemical barriers include melanin and acids.
3. The skin is a sense organ with touch, pressure, pain, and temperature receptors. These receptors receive the stimuli and then send messages to the brain.
4. Endocrine. The skin is the place for the production of the precursor of vitamin D. The vitamin D is a hormone that helps to control the calcium concnetration in the blood.
5. Metabolic. The skin plays a small role in making proteins and detoxifying chemicals.
6. Excretion. The skin is an important excretory organ and supports the kidneys in regulating salt, urea and water elimination.
7. Blood reservoir. About 5% of the blood volume is stored in the skin.