Lecture 19 - Skin Structure And Function

Question 1

Other term for the Skin

Answer 1

The integumentary system

Question 2

General Structure of the skin (Macroscopic)
3 layers

Answer 2

Epidermis
Dermis
Hypodermis

Question 3

Primary functions of the skin

Answer 3

-Protection and repair
-Thermoregulation and excretion of waste (ions)
-Lubrication (sebaceous glands release oil onto surface
-Energy storage (Hypodermis)
-Vitamin D synthesis
-Absorption (water, O2)
-Aesthetics (communication, attraction)
-Sensation (has receptors)

Question 4

What are the 4 layers in the Epidermis?

Answer 4

Stratum Corneum
Granular Layer
Stratum spinosum
Basal cell layer

Question 5

What is the extra layer of cells in thick skin?

Answer 5

Stratum lucidum
A transparent layer ONLY on Palms and Soles of feet

Question 6

How are cells held together laterally in the epidermis?

Answer 6

Adherens junctions

Question 7

How are cells/layers held together Basically/Apically?

Answer 7

By desmosomes

Question 8

Function of epidermis

Answer 8

Prevent water loss (keratinised layer of squames)
Prevents pathogenic entry
Synthesis keratin

Question 9

What is the Stratum Corneum?

Answer 9

Outermost layer (made of dead keratinocytes/squames)
Continuously sheds

Question 10

Granular layer structure (What type of cell? What does it contain?)

Answer 10

Stratfied squamous epithelial cells
Lamellar bodies (contain lipids needed to form water barrier)
Tonofibrils and Keratohyalin granules (Make keratin matrix)

Question 11

Stratum spinosum (what does it do and what does it contain? What type of cell?

Answer 11

Cuboidal epithelium
Produces lamellar bodies
Langerhans cells/Epidermal dendritic cells = Macrophage of the skin most prominent here

Question 12

Basal cell layer structure and function, what type of clell?

Answer 12

Tall columnar epithelial cells
Where keratinocytes are produced
As keratinocytes differentiate they migrate away from basal layer towards Stratum Corneum
Make intermediate keratin filaments called TONOFILAMENTS
Where Melanocytes are found

Question 13

3 Layers of the dermis

Answer 13

Papillary layer = Upper layer (Nipples of skin here)

Reticular layer - Lower layer (has appendages of skin, hair, sebaceous glands , sweat glands, blood vessels)

Dermal papillae - Region between ridges of epidermis and dermis

Question 14

Dermis functions:

Answer 14

Is IRREGULAR DENSE CONNECTIVE TISSUE
Hairs and Sweat glands = Thermoregulation
Contains sensory structures (mechanoreceptors)’
Gives structure to the skin and so body shape

Question 15

Where is the Hypodermis?

Answer 15

Lowest layer of skin (not considered part of the skin though)

Question 16

Structure of the Hypodermis

Answer 16

Mainly adipose tissue
Loose connective tissue so contains fibroblasts/macrophages and protein fibres

Question 17

Functions of the Hypodermis

Answer 17

Energy storage
Insulator for heat generated from muscles
Shock absorption
Connects skin to muscles and bone underneath
Makes hormones like leptin (appetite)

Question 18

What do Keratinocytes do?

Answer 18

Make Keratin

Question 19

What are Rete ridges?

Answer 19

The ridges/protrusions of the epidermis into the dermis

Question 20

Mucous Membranes structure (3 layers)

Answer 20

Epithelial layer (cells attached to basal Lamina)
Lamina Propria (connective tissue, blood capillaries, lymph vessels)
Muscularis Mucosae (Smooth muscle fibres)

Question 21

What is a skin appendage?

Answer 21

Skin associated structures that serve a particular function

Question 22

List 4 skin appendages

Answer 22

Hair follicles
Sebaceous glands
Sweat glands
Nails

Question 23

2 Main types of hair

Answer 23

-Vellus (Replaces Languo hairs that are only present on the developing fetus)
-Terminal

Question 24

Vellus hair structure/features

Answer 24

Short
Thin
Light coloured
Soft

Question 25

Terminal Hair structure/features

Answer 25

Long Wide Dark Coarse

Question 26

Where are Vellus hairs found around the body?

Answer 26

Over most surfaces NOT on palms, soles of feet, glans penis and glans clitoris etc…

Question 27

Where are Terminal hairs found?

Answer 27

Head (scalp, eyebrows, nasal passage) Axillae = armpit External genital region

Question 28

Hair functions

Answer 28

Thermoregulation Sexual Attraction Sensation Protection

Question 29

Hair in Thermoregulation

Answer 29

Arrector pilli muscles contract when cold to make hair stand up Act as partial barrier to UV

Question 30

Hair in sexual attraction

Answer 30

Hairs trap oils secreted by Apocrine Sweat Glands Oils attract opposite sex

Question 31

Hairs in Sensation

Answer 31

Have sensory nerve endings in bulb Detects air movement/vibrations Provides sensory awareness

Question 32

Hair in Protection

Answer 32

Prevent entry of dust and pathogens in body Eyebrows reduce amounts of light and sweat entering eyes Axilla hair (armpit) removes sweat from the body

Question 33

What type of muscle fibres do arrector pili muscles consist of?

Answer 33

Smooth

Question 34

What type of Gland in terms of secretion is the Sebaceous gland?

Answer 34

Holocrine gland

Question 35

What does the Sebaceous gland produce?

Answer 35

Sebum (oily waxy substance)

Question 36

Functions of sebaceous gland

Answer 36

Lubricate skin and hair Reduce water loss from skin and hair Reduce damage of epidermis from friction Protect from moisture and UV damage

Question 37

Where are sebaceous glands found?

Answer 37

Face and Scalp Eyelids Penis Labia Nipples Lip

Question 38

Are sweat glands Endocrine or exocrine glands?

Answer 38

Exocrine Secrete substances (Sweat) via a duct onto epithelial cells

Question 39

2 Types of sweat gland

Answer 39

Eccrine Sweat glands Apocrine sweat glands

Question 40

Where are Eccrine sweat glands found and their purpose?

Answer 40

All over the body Cooling

Question 41

Where are apocrine sweat glands found and their purpose?

Answer 41

Mainly axilla (Armpit) Perianal areas Produces sweat that has odor once activated (pheromones)

Question 42

Location of Nails

Answer 42

Distal surface of phalanges (fingers and toes)

Question 43

Nail structure

Answer 43

Made of Alpha keratin Nail plate Nail matrix Nail bed

Question 44

Functions of nails

Answer 44

Protection of distal phalanx Enhances precise delicate movements A tool (extended precision grip) e.gg pull splinter out

Question 45

Types of Mechanoreceptors found in the skin

Answer 45

End bulbs Free nerve endings Tacitle discs (Merkel discs/corpuscle and Meissner discs) Pacinian corpuscle Ruffini’s corpuscle Root hair plexus

Question 46

What do End Bulbs detect?

Answer 46

A Thermoreceptor TEMPERATURE

Question 47

What do free nerve endings detect?

Answer 47

Pain (Have nociceptors)

Question 48

What do Meissner corpuscles detect?

Answer 48

Light touch, vibration

Question 49

What frequency of vibration do Meissners’ corpuscles detect?

Answer 49

Between 10 to 50Hz

Question 50

What do Pacinian Corpuscles detect?

Answer 50

Pressure/vibration

Question 51

What frequency of vibration do Pacinian corpuscles detect?

Answer 51

Between 100-1000Hz

Question 52

What do Krause end bulbs detect?

Answer 52

Cold temperature

Question 53

What do Ruffini’s corpuscles detect?

Answer 53

Joint movements and tissue stretch

Question 54

What do merkel cells/discs detect?

Answer 54

Light touch

Question 55

What are the 2 types of skin?

Answer 55

Hairy Skin (Thin) Non-Hairy Skin (Thick)

Question 56

What are the exceptions to the rule of Hairy skin being thin and non hairy skin being thick?

Answer 56

Lips Back of pinna Some areas of external genitalia

Question 57

Where is Non-Hairy (Thick) skin located?

Answer 57

Palmar surface of hands Plantar surface of feet Area between fingers and toes

Question 58

Structure of Non-Hairy (Thick) skin

Answer 58

No hair follicles No sebaceous glands NO arrector pili muscles THICK Stratum Corneum Stratum lucidum present (transparent layer only in thick skin) Pronounced/large rete ridges Regular shaped Dermal papillae

Question 59

Thin (Hairy) skin structure

Answer 59

Hair follicles present (Vellus and/or terminal) Sebaceous glands Arrector pili muscles Smaller rete ridges Irregular shaped dermal papillae NO STRATUM LUCIDUM

Question 60

How to differentiate between Hairy (Thin) and Non-Hairy (Thick) skin

Answer 60

Non hairy/ thin = deep rete ridges and extended dermal papillae Thick skin = thinner dermis but thicker Stratum Corneum in epidermis

Question 61

How is the structure of Non-hairy (thick) skin relevant to its function

Answer 61

Prevent tissue loss due to abrasion (thick stratum Corneum) Increased friction between skin and surfaces (No sebaceous glands so no lubricating sebum) Increased sensation (MANY mechanoreceptors)

Question 62

Where are Melanocytes located?

Answer 62

Basal cell layer

Question 63

What are melanosomes?

Answer 63

Organelles produced by melanocytes

Question 64

What do melanosomes do?

Answer 64

Synthesis melanin

Question 65

What is the function of melanin?

Answer 65

Covers the nuclei of cells in the Epidermis to protect DNA from UV damage (Stops formation of Thymine dimers)

Question 66

What are Langerhans cells?

Answer 66

Macrophages residing in the epidermis They are dendritic cells (present pathogenic antigens to Reticuloendothelial system)

Question 67

Where are Langerhans cells found?

Answer 67

Most prevalent in Stratum spinosum