Integumentary system

Question 1

Describe the skin

Answer 1

• largest organ
• constitutes almost 8-20% of body mass
• has a surface area of approximately 1.6 to 1.8 m2

Question 2

3 major skin layers

Answer 2

Epidermis - most superficial
Dermis - deep layer
Hypodermis - deepest layer with loose connective and adipose tissue

Question 3

skin functions

Answer 3

• acts as a protective barrier that limits the migration of microbes and chemicals into the body
• thermoregulation as it participates in evaporation in hyperthermic environments
• neurons in the skin detect sensory input that helps with interacting with the environment

Question 4

describe epidermis (uppermost skin layer) layers

Answer 4

from deep to superficial, it consists of five layers;
- basal layer (stratum basale/germinativum)
- prickle cell layer (stratum spinosum)
- granular layer (stratum granulosum)
- clear layer (stratum lucidum)
- cornified layer (stratum corneum)

Question 5

explain difference in skin in the palms and soles

Answer 5

• epidermis is significantly thicker in the regions of the palms and soles
• there are no sebaceous glands or hair follicles
  skin in the palms and soles are therefore called glabrous skin

skin elsewhere is referred to as hirsute (hairy) skin
- stratum lucidum (clear layer) is absent from hirsute skin but present in glabrous skin

Question 6

cell types in epidermis

Answer 6

Keratinocytes - squamous epithelial cells that originate from basal stem cells; continuously mature from basal to corneum layer and desquamate

Melanocytes - synthesize melanin that gives color to the skin and protects it from ultraviolet radiation

Langerhans cells - antigen presenting cells

Merkel cells - mechanoreceptors

Question 7

Describe dermis

Answer 7

• deep to the epidermis
• irregularly arranged and filled mostly with connective tissue
• lies deep to the basement membrane of the stratum basale
• ## collagen (85% type I and 15% type III) and elastic fibers that facilitate recoil of the skin, held together by a mixture of glycoproteins, bound water and glycosaminoglycans

Question 8

dermis layers

Answer 8

• papillary layer: superficial, characterized by dermal papillae, less abundant and smaller in thin skin that has minimal mechanical stress, in areas of thicker skin, they tend to form curved parallel lines. type III collagen
• reticular layer: deep, no clear demarcation, mostly coarse type I fibers with variable number of elastic fibers

Question 9

describe hypodermis

Answer 9

• subcataneous tissue, a layer of adipose tissue attached to the deep aspect of the dermis
• increases mobility of skin, it thermally insulates body, acts as a shock absorber and and is a source energy
• filled with subcataneous nerves, vessels and lymphatics
• contains smooth muscles erector pili that serves to connect deep part of hair follicle with superficial dermis

Question 10

Importance of hair
and 2 types

Answer 10

Hairs are important in sensing, thermoregulation and protection against injury and solar radiation.

• Vellus hairs do not project beyond their follicles in some of the areas, however, they are short and narrow and cover most of the surface of the body
• Terminal hairs are longer, thicker and more heavily pigmented. They are mostly observed on males but also in the axillary and pubic regions of both sexes.

Question 11

What is a hair follicle?

Answer 11

The sac containing the hair out of which it grows
It’s a downgrowth of the dermis and contiguous with the epithelium

Question 12

What is the hair bulb?

Answer 12

The lowest expanded extremity of the hair follicle that fits like a cap over the dermal hair papilla enclosing it

Question 13

Transverse cut of hair layers
From outermost to innermost

Answer 13

Connective tissue heath
External root sheath
Cuticle
Cortex
Medulla

Question 14

Describe nails ( structure)

Answer 14

Nails are homologous to the stratum corneum of the epidermis and contain a variety of minerals, such as calcium.
They consist of compacted and layered keratin-filled squames (scales).

Question 15

Describe sweat glands

Answer 15

Sweat glands are small, tubular structures located in the skin. They are exocrine glands; secrete substances on the epithelial surface via ducts. They produce sweat, important for thermoregulation.

There are two types of sweat glands:
Eccrine sweat glands(The majority) : They are long, unbranched, tubular structures with a highly coiled secretory portion situated deep in the dermis. A narrower duct emerges from the gland and it opens via a pore on the skin surface.

Apocrine sweat glands:
are large glands located in the axillae, perianal region, nipples, periumbilical region, prepuce, scrotum, mons pubis, labia minora, nail bed, penis and clitoris.
- also consist of a secretory coil. However, the duct emerging from the gland opens inside the pilary canal above the duct of the sebaceous gland or directly on the surface of

Question 16

Describe sebaceous glands

Answer 16

Sebaceous glands are small saccular structures located in the dermis, which cover most of the body. They consist of a cluster of secretory acini, which is continued by a duct which opens into the dermal pilary canal of the hair follicle.

The ducts can also open directly on the surface of the skin, as seen on the lips and buccal mucosa. Sebaceous glands secrete sebum, which is an oily and fatty secretion. Sebum is crucial in the epidermal barrier and the skin’s immune system.