Skin (Integumentary System)

Question 1

What are the functions of the integumentary system?

Answer 1

1. protects your inner organs and it is in need of daily care and protection to maintain its health.
2. Protects the body
   from: invasion by microorganisms and other environmental factors,
   Wear and tear from contact with grit, microbes, or harmful chemicals,
   DNA damage caused by UV radiation
3. Prevent dehydration: layers of keratin and glycolipids in the stratum corneum
4. Acts as a sensory organ
5. Maintains temperature and electrolyte balance
6. Synthesizes vitamin D
7. Underlying hypodermis stores fats, protects underlying structures, provides insulation

Question 2

Overview of the integumentary system

Answer 2

1. Composed of skin and its accessory structures
2. 16 percent of body weight and covers an area of 1.5 - 2 m2 in an adult human body
3. largest organ system in the human body

Question 3

What is the structure of the integumentary system?

Answer 3

Divided into three main regions
Epidermis: avascular, thinnest, most superficial layer
Dermis: well-vascularized, contains components associated with skin function
Hypodermis: well-vascularized, loose connective tissue which anchors it to underlying structures
made of multiple layers of cells and tissues
Communicates with the brain via sensory, autonomic and sympathetic nervous systems

Question 4

In the epidermis what is the difference between thick and thin skin?

Answer 4

Thick skin:
Contains 5 layers: includes stratum lucidum
Appearance: Friction ridges (tire treads, prints)
Function: sensation, manipulation of objects
Location: palms of hands and soles of feet

Thin skin:
Contains 4 layers: stratum lucidum is absent
Appearance: Smooth with irregular grooves
Function: Normal skin function
Location: found in most locations throughout the body

Question 5

What cells are in the epidermis?

Answer 5

Basal cells, Keratinocytes, Merkel cell, Melanocytes and Langerhans cells (dendritic cells)

Question 6

What are the functions and locations of the cells in the epidermis?

Answer 6

Basal cells: cuboidal stem cell that produces keratinocytes
Location: Stratum basale

Keratinocytes: cells that manufactures and stores the protein keratin and water-repelling glycolipid that helps prevent water loss from the body
Location: stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Merkel cell: touch receptor for sensory nerves, especially abundant on surfaces of hands and feet
Location: Stratum basale

Melanocytes: cell that produces the melanin pigment, which gives hair and skin its color, and protects the epidermis from ultraviolet (UV) radiation damage
Location: Stratum Basale

Langerhans cells (dendritic cells): Macrophages that destroy bacteria, foreign particles, and damaged cells 
Location: Stratum spinosum

Question 7

Layers of the epidermis (top-bottom)

Answer 7

Stratum Corneum, Stratum Lucidum, Stratum Granulosum, Stratum Spinosum and Stratum Basale (Stratum germinative)

Question 8

Stratum Basale (stratum germinativum)

Answer 8

single layer of stem cells that constantly produces new cells which is then pushed towards to surface
attaches the epidermis to dermis via basal lamina, basement membrane intertwining collagen fibers

Question 9

Stratum Spinosum

Answer 9

looks spiny due to presence of desmosomes with interlock with each other and strengthen the bond between the cells
8-10 layers of keratinocytes rich in RNA to produce keratin

Question 10

Stratum Granulosum

Answer 10

grainy appearance due to accumulation of keratin granules

3-5 layers of flat cells with thicker cell membranes: nuclei and other organelles disintegrate as cells die

Question 11

Stratum Lucidum

Answer 11

smooth, seemingly translucent thin layer

found only in the thick skin of palms, soles, and digits

Question 12

Stratum Corneum

Answer 12

15 - 30 layers of dry, dead cells filled with keratin.

most superficial layer: exposed to external

Question 13

Melanocytes

Answer 13

cells that produce melanin

Question 14

Melanin

Answer 14

pigments that give skin its color

Question 15

Melanosomes

Answer 15

vesicles of melanin produced by melanocytes

Question 16

Properties of Melanin

Answer 16

• Provide color to hair and skin, and protects
• DNA damage caused by ultraviolet radiation.
• Melanin occurs as eumelanin (black and brown) and pheomelanin (red).
• Dark-skinned individuals produce more melanin than those with pale skin.
• Too little melanin can cause DNA damage of epidermal cells and folic acid destruction
• Too much melanin can reduce vitamin D production, an important nutrient involved in calcium absorption

Question 17

Explain how tanning occurs over the course of seven days

Answer 17

1. Prolonged exposure to ultraviolet (UV) radiation in sunlight
2. Melanocytes increase melanin production
3. skin color darkens
   melanin in nuclear cap absorbs UV radiation before it reaches DNA. Increased apoptosis of UV damaged cells
4. If cells are NOT protected by melanin, UV radiation reaches the nucleus to cause severe damage, eg skin cancer

Question 18

Why do tans not last?

Answer 18

1. Melanosomes are eventually destroyed by fusion with lysosomes;
2. Melanin-filled keratinocytes in the stratum corneum eventually slough off

Question 19

What is the location and structure of the Dermis?

Answer 19

Location: deep to the epidermis

Structure: 2 layers of connective tissue of an interconnected mesh of elastin and collagenous fibers with fibroblasts, blood and lymph vessels, adipocytes, phagocytes, nerves, hair follicles, sweat glands, touch receptors (Meissner corpuscles)
Papillary Layer: superficial layer of loose, areolar connective tissue which forms finger-like dermal papillae to increase connection strength with epidermis
Reticular Layer: Deeper, thicker layer of dense, irregular connective tissue which provide elasticity, structure and tensile strength. Collagen binds to water to keep the skin hydrated

Question 20

What is the location, structure, and function of the Hypodermis (subcutaneous layer or superficial fascia)?

Answer 20

Location: lies directly below dermis to connect skin to underlying fascia (fibrous tissue) of bones and muscles. Not strictly a part of skin

Structure: well-vascularized, loose, areolar connective tissue and adipose tissue

Function: fat storage, insulates and cushions the integumentary system

Question 21

What is the structure and function of hair?

Answer 21

Structure: keratinous filament growing out of the epidermis made of dead, keratinized cells.

Functions: protection, sensory input, thermoregulation, and communication.
protects the skull from the sun, traps and excludes particles containing allergens and microbes.
hair root plexus senses air movement or other environmental disturbances
arrector pili (smooth muscle) connected to hair root contracts to cause goosebumps which makes the external hair shaft “stand up” and trap a layer of air to add insulation.

Question 22

What is the structure and function of nails?

Answer 22

Structure: nail body is formed from densely packed dead keratinocytes and rests on the nail bed

Functions: protects tips of fingers and toes from maximum mechanical stress due to their location (farthest extremities). Also forms a back-support for picking up small objects with the fingers.

Question 23

Sweat glands are a type of…

Answer 23

Merocrine exocrine gland

Question 24

What are the different types of glands and their locations?

Answer 24

Sudoriferous glands: produce watery sweat to cool the body (thermoregulation)

Eccrine sweat gland: releases sweat via pores
Type of sweat: hypotonic sweat
Location: all over the body, mostly associated with hair follicles

Apocrine sweat gland: releases sweat into hair follicles.
Type of sweat: Thicker sweat due to organic compounds which can be decomposed by bacteria and smell
Location: hair follicles in densely hairy areas (armpits and genital regions)

Sebaceous Gland: produces lipid sebum onto the skin surface.
Function: lubricates and waterproofs skin and hair, antibacterial properties
Location: all over the skin’s surface, abundant on palms, soles, forehead.

Question 25

What are the sensory receptors of the integumentary system and their locations?

Answer 25

Merkel cells and tactile (Meissner) corpuscle: senses light touch. Located superficially, just below epidermis

Lamellar (Pacinian) corpuscle: senses deep pressure and vibration. Located deeper, in hypodermis

Nociceptors: detect pain (extreme sensation) to prevent damage to structures

Thermoreceptors: detect EITHER hot or cold temperatures

Question 26

What are the motor functions of the integumentary system

Answer 26

Regulated by the sympathetic nervous system
Controls sweat production, superficial blood flow and arrector pili muscles
When the arrector pili muscle contracts, it pulls the follicle and hair into a more upright position and causes a “goose bump” around the hair shaft

Question 27

How does thermoregulation work in the integumentary system?

Answer 27

In response to high external temperature and/or vigorous activity
superficial blood vessels dilate, increasing blood flow to the skin and allowing dissipation of heat, especially in hot weather→ skin redness
0.7 -1.5 L of sweat can be produced per hour

In response to a drop in body temperature or low external temperature
superficial blood vessels contract, restricting blood flow to the skin (& extremities) and pushing blood to the internal organs → whitish skin

Question 28

What organs are involved in vitamin D production?

Answer 28

skin, liver & kidney

Question 29

What is the first step in vitamin D production?

Answer 29

The first step of the pathway requires skin exposure to UV light: This first step can be prevented by too much melanin (which blocks UV rays) or by the application of too much sunscreen

Question 30

Functions of vitamin D

Answer 30

essential for the normal absorption of calcium and phosphorous to sustain healthy bones. essential for general immunity against bacterial, viral, fungal infections.
It May help prevent cancer