Chapter 5: The Integumentary System

Question 1

The integumentary system

Answer 1

Function: to cover the entire outer surface of the body

Includes: skin, hair, nails, certain glands, and sensory receptors

Question 2

Skin functions

Answer 2

Functions:
- protects the body from injuries, mold/bacterial invasion, UV damage, and dehydration
- acts as a receptor for sensory input
- regulates body temp (sweat glands)
- secretes waste (salts, water, urea)
- creates vitaminD from cholesterol when under sunlight

Question 3

What are the structures of the skin?

Answer 3

2 layers:

1) the epidermis (upper layer)
2) the dermis (lower layer)
3) the subcutaneous layer (fat layer under dermis)

(Note - the subcutaneous layer is not part of the skin, but it helps to support the skin)

Question 4

Epidermis

Answer 4

Composed of keratinized stratified squamous epithelium. It will renew itself every 30-40 days

Contains 4 major cells and 5 cell layers:

4 Cells - Keratinocytes, Melanocytes, Langerhans cells, Merkel cells

5 Cell layers - Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum

Question 5

Keratinocytes

Answer 5

90% of the epidermis

Functions:
- Produces keratin (fibrous protein)
- protects skin and underlying tissues from heat and chemicals

(Note: the surface cells are dead and only contain keratin)

Question 6

Melanocytes

Answer 6

8% if the epidermis

Function:
- will secrete melanin to keratinocytes

• made of spider-shaped epithelial cells
• found near the basal surface of their cell

Question 7

Langerhans cells

Answer 7

Function:
- alert other immune cells about potential invaders

(Note: they come from red bone marrow and make their way into the epidermis)

Question 8

Merkel cells

Answer 8

Function:
- help with touch sensations, and contacting sensory neurons

(Found deep in the epidermis)

Question 9

Stratum basale

Answer 9

Deepest layer which is attached to the dermis by the wavy border

Contains a single row of cuboidal/columnar keratinocytes. As well as melanocytes and Merkel cells

Function: help in renewing the epidermis by constantly going through mitosis (pushing up new cells)

Question 10

Stratum spinosum

Answer 10

Contains 8-10 layers of keratinocytes. Also Langerhans cells and melanocytes.

Function:
- provide structural support
- fight against invaders (using langerhans cells)

Question 11

Stratum granulosum

Answer 11

Contains 3-5 layers of flattened keratinocytes; the cells will lose their nucleus and organelles (apoptosis)

Also contains keratohyalin protein and lamellar granules which release lipid, water-repellant secretions.

Function: it is the transition layer between living cells below and dead cells above.

Question 12

Stratum lucidum

Answer 12

Present on in thick skin (palms/soles).

Consists of 3-5 layers of clear, flat, dead keratinocytes

Question 13

Stratum corneum

Answer 13

The outermost layer of skin

Contains 25-30 layers of dead keratinocytes

The lamellar secretions between cells allow for this layer to be waterproof.

Question 14

Keratinization

Answer 14

The accumulation of more and more protective keratin.

This occurs as more cells move from the deepest layer to the surface layer.

Question 15

Dandruff

Answer 15

An excess of keratinized cells that shed from the scalp

Question 16

Dermis

Answer 16

Connective tissue with fibroblasts, adipocytes, macrophages, mast cells, and many fibres.

Contains blood vessels, hair follicles, glands, and nerves.

2 regions:
1) Papillary region
2) Reticular region

Question 17

Papillary region

Answer 17

It is the upper 1/5th of the dermis

Contains dermal papillae at the junction with the epidermis. These papillae contain capillaries, nerve endings, and Meissners corpuscles (which help transmit touch sensations)

Question 18

Reticular region

Answer 18

The lower portion of the dermis.

Contains collagen fibres which give skin strength and bind water to keep hydrated, elastic fibres which provide stretch recoil.

Contains pacinian corpuscles (which help for vibration and pressure sensations)

Question 19

Melanin

Answer 19

Produced by melanocytes; contributes to skin colour.
- amount of melanin produced deciphers colour
- more melanin = more UV protection
- melanin is a buffer that protects our keratin by absorbing UV rays

Question 20

Albinism

Answer 20

An inherited inability to produce melanin.

Question 21

Vitiligo

Answer 21

Partial or complete loss of melanocytes from patches of skin

(Michael Jackson)

Question 22

Hair (or pili)

Answer 22

Present of most skin surfaces (includes eyelashes, eyebrows)

Hair shaft = the visible portion
Hair root = embedded in skin

Hairs can provide slight touch sensations since they have nerve endings attached.

Question 23

Hair shaft / root structure

Answer 23

Contains 3 rings of dead keratinized cells:
1) medulla - core of large cells
2) cortex - several layers of flattened cells
3) cuticle - single layer of cells that overlap one another.

Hair pigment: controlled by melanocytes at base of the follicle

Question 24

Hair follicle

Answer 24

A tube-like pocket of epidermis that extended into the dermis.

Hair bulb = base of follicle
Hair papilla = protrudes into bulb and contains capillaries and layers of cells called the matrix.
(These matrix cells divides as hair grows and new king created cells move upwards pushing the old dead cells up and out of the epidermis)

Question 25

Hair growth cycle

Answer 25

Growth stage - cells of matrix are dividing
Regression stage - matrix cells stop dividing
Resting stage - nothing happens

(After resting stage, old hair root falls out of follicle and new hair grows)

Question 26

Arrector pili muscle

Answer 26

Smooth muscle which attaches to the hair follicle and raises the hair.

Question 27

Sweat glands

Answer 27

2 types:
1) Eccrine - a coiled tubular gland emptying into a pore. Helps to regulate body temp. Found in forehead, palms…etc), functions from birth.

2) Apocrine - larger, and empty into hair follicles. Found on head and groin, only starts it function at puberty

Question 28

Ceruminous glands

Answer 28

Modifies apocrine glands found in skin lining the external ear canal which secretes ear wax.

Question 29

Sebaceous glands

Answer 29

Alveolar glands connected to hair follicles which secrete sebum which helps soften and lubricate the hair and skin.

Question 30

Nails

Answer 30

Hard, keratinized epidermal cells.
Consists of:
1) Free edge - extends over digit (white part)
2) Nail body - the visible portion attached to digit
3) Nail root - embedded in skin fold

Question 31

Nail bed

Answer 31

The skin that is under the nail found in the deeper layers of the epidermis

Question 32

Nail matrix

Answer 32

Responsible for nail growth by constantly undergoing mitosis to produce more keratin nail cells.

Question 33

Special functions of the skin

Answer 33

1. Body temp regulation:
   - changes in temp slow down metabolic processes, so the surface of the skin stands against the temp. And sweat glands provide evaporative cooling.
2. Vitamin D synthesis:
   - begins in the skin using cholecalciferol which helps increase calcium absorption