Introduction Physiology

Question 1

What are the main integumentary components of the integument?

Answer 1

Cutaneous membrane structures
- Epidermis and dermis layers

Accessory organs/structures

• Hair and nails
• Exocrine/sebaceous and sweat glands
• Sensory receptors and nerve fibers
• Cutaneous plexus

**hypodermis is not part of the integument and separates the integument from the deep fascia

Question 2

The three skin layers of the integument

Answer 2

1) epidermis
- derived from ectoderm
- composed of stratified squamous epithelium with outer keratinization layer
- purpose is to create a multi-purpose barrier between internal and external environments

2) dermis
- derived from mesoderm
- composed of connective tissues and gives skin its strength and elasticity
- also contains sensory nerves and blood vessels and its job is to provide sensation and blood supply to the dermis

3) hypodermis (subcutaneous layer)
- NOT part of the integument technically
- contains nerves/blood and lymph vessels as well as 50% of total body fat
- function is to facilitate mobility of the skin and contribute to thermal insulation

Question 3

What are the two types of skin?

Answer 3

Thick and thin skin

• thick = >5mm thick palms/and soles of feet and has thicker epidermis
• thin = 2-3mm thick with narrow epidermal ridges (finger tips)

Question 4

What are common age related changes seen in the integument?

Answer 4

Fewer melanocytes

Drier/thinning epidermis

Reduced blood supply and slower skin repair

Altered hair and fat distribution as well as fewer active follicles

Decreased perspiration

elderly people are also more prone to heat stress due to impaired blood flow and atrophy of the subcutaneous fat

Question 5

Two types of hair

Answer 5

Terminal hairs

• large, coarse, dark pigmented
• includes scalp and armpit hair

Vellus hairs

• smaller, shorter and delicate
• found on the general body surface

Question 6

What is the hair called on neonates?

Answer 6

Lanugo

• is super thin and unpigmented
• replaced with vellus hairs shortly after birth

Question 7

Hair regions and associated structures

Answer 7

Hair shaft:
- begins deep within hair follicle

Hair root:

• anchors the hair into the skin
• includes the hair bulb which is the bottom-most portion of the root and is where new hair is generated

Root hair plexus
- collection of sensory nerves that surround the base of the follicle

Arrector pili

• smooth muscle attached to hair folllicles
• contract hair when activated

Question 8

Structures associated with nails

Answer 8

1) nail body
- visible portion of nail and is bordered by lateral nail grooves and nail folds
- covers the nail bed which is the underlying epidermis

2) lunula
- pale crescent part of the proximal nail body

3) nail root
- epidermal fold where nail production occurs

4) eponychium
- portion of the stratum corners of the nail root that extends over exposed nail

5) hyponychium
- area of thickened stratum corneum under the free edge of the nail

Question 9

What are the three types of exocrine secretions used by the integumentary exocrine glands?

Answer 9

1) merocrine secretion
- releases membrane-bound secretory vesicles

2) apocrine secretion
- “pinches” off portions of the rim of cells in order to secrete secretory products

3) holocrine secretion
- mature cell dies and becomes the secretory product itself

Question 10

Sebaceous glands

Answer 10

Holocrine glands that discharge sebum onto the hair follicules and skin surface
- contractions of arrector pili muscle causes the release of sebum

Sebum = mixture of triglycerides, cholesterol, proteins and electrolytes and consists of some antimicrbial properties

Question 11

Apocrine vs merocrine sweat glands

Answer 11

Apocrine

• compound coiled tubular glands w/ large secretory acini
• limited to axilla, groin and nipples
• secretes contents into hair follicles
• produces viscous/sticky cloudy and odorous secretions
• possible function in olfactory communications
• strongly influenced by hormones
• **does NOT contribute to temperature regulation

Merocrine

• simple coiled tubular glands
• found pretty much everywhere (highest number is on palms and soles)
• small secretory acini
• produce water secretions with electrolytes
• controlled by the nervous system
• secrete contents onto skin surface directly
• important in thermoregulation and antibiotic properties

Question 12

Receptors in the dermis

Answer 12

Meissner corpuscles

• mechanoreceptor
• found in the papillary layer
• detect light touch pressure and vibrations

Lamellated (Pacinian) corpuscles

• mechanoreceptor
• found in dermal and hypodermis layers
• detect deep pressure and vibration

Ruffini corpuscles

• mechanoreceptor
• found in the reticular layer
• sensitive to pressure and stretching of skin

Question 13

Receptors in the epidermis

Answer 13

Free nerve endings

• found between epidermal cells
• sensitive to touch and pressure

Tactile (merkel) discs

• found in the deepest layer of the epidermis (basale)
• detects texture and steady pressure

Question 14

Barrier function of the skin

Answer 14

Shields against UV radiation and mechanical damage
(physical shield)
- also fungi/bacteria and viruses (microbial shield)
- also against allergens and irritants. (chemical shield)

Question 15

Immunity functions of the skin

Answer 15

Activates mast cells, macrophages and APCs (dermal dendrocytes) as well as fibroblasts

Releases histamine, PGE, leukotrienes, cytokines
- this dilates the blood vessels and increases capillary permeability

Question 16

Convection

Answer 16

Heat transfer through a fluid or gas that carries heat between the body and environment

• caused by molecular motion
• usually water or air
• *convective heat loss is proportional to the difference between skin and ambient temperature

Question 17

Radiation

Answer 17

Energy that is radiated or transmitted in the form of rays or waves/particles

• occurs between skin and solid bodies in theenvironment
• *rate is proportional to the temperature difference between the skin and the object

Question 18

8 primary functions of the skin

Answer 18

Protection from injury

Barrier to prevent dehydration

Regulation of body temperature

Non-specific defensive barrier to microorganisms and immunocompetent dendritic cells

Excretion of salts

Synthesis of vitamin D

Sensory organ to the external environment

Sexual signaling

Question 19

What are the three phases of hair and nail growth

Answer 19

1) growth (anagen) phase
2) regression (catagen) phase
3) resting (telogen) phase

Question 20

What are the 2 layers of hair growth?

Answer 20

1) matrix zone = mitotic activity occurs

2) keratogenous zone = keratinization of hair cells occurs

Question 21

What layer of the skin forms the hyponychium and eponychium of the nail?

Answer 21

Stratum corneum layer

Question 22

What are two common nail shape variants that are highly linked to specific diseases?

Answer 22

Pitted or distorted nails = check for psoriasis

Nail clubbing = check for blood or pulmonary disorders (some type of anemia or chronic hypoxia)

Question 23

What are the three cell types in merocrine (eccrine) sweat glands?

Answer 23

Basal clear cells:
- secrete water and electrolytes

Apical dark cells:

• secrete glycoproteins and defensins.
• secretes cathelidicin and dermicidin

Myoepithelilal cells
- only function to increase contractile activity of the other two cells

Question 24

How does the perception of pain work?

Answer 24

Acute inflammation causes injuried cells to release chemical mediators which includes substance P.
- substance P both activates nerve ending nociceptors and also triggers degranulation of mast cells of histamine to induce vasodilation

Question 25

Conduction

Answer 25

Heat transfer between a body and a solid material of different temperature (ice, hot sand, etc.) - minimal heat gain or loss under most normal condtions

Question 26

Evaporation

Answer 26

Heat transfer via a liquid (sweat) being directly converted into a gas and releasing energy - *rate is independent of the temperature gradient between skin and environment

Question 27

What are glomus bodies?

Answer 27

Arterial-venous anastomoses that are found in the skin - apical skin = very high density - nonapical skin = very low density and gains most blood flow via capillaries

Question 28

Difference between preganglionic and postganglionic sympathetic fiber actions on skin

Answer 28

Preganglionic - releases ACh - causes vasodilation and formation of bradykinin Postganglionic - releases NE - causes vasoconstriction * strong sympathetic activity causes mass vasoconstriction and diaphroetic skin (cold clammy and sweaty)

Question 29

Where are the primary temperature-sensitive neurons located?

Answer 29

In the preoptic area/ganglion - are warm sensative neurons which promote sweating and vasomotor dilation - receives inputs from skin temperature thermoreceptors Dorsomedial hypothalamus - are cold sensative neurons and receive inputs form skin temperature thermoreceptors - generates thermogenesis command neurons - shiver of the skeletal muscle fibers - increased thermogenesis of the Brown adipose tissues **both of these antagonize each other based on thermoreceptor inputs from skin

Question 30

What nucleus of the hypothalamus controls body temperature?

Answer 30

Anterior hypothalamus - regulates body temperature and controls sympathetic nervous system that innervates cutaneous AVMs and vasodilator or constricts based on what is needed. **skin temperature is directly proportional to blood flow of the skin**

Question 31

What receptor in cellular membranes allows H+ ions to bypass ATP synthase and generate heat rather than ATP?

Answer 31

UCP1 | - upregulated in cold temperatures

Question 32

CF and sweating

Answer 32

Defective CFTR receptors prevent the ability to reabsorb chloride ions before seat comes out of the merocrine sweat glands - the inability to reabsorb chloride causes a major increase in negative charge which prevents sodium from being reabsorb as well leading to salt loss and salty sweat.

Question 33

How does skin regulate vitamin D

Answer 33

Sunlight upregulates natural 7-dehydrocholesterol production in the skin - this leads to secosterol -> cholecalciferol production (Vitamin D3) - vitamin D3 enters the liver and then the kidneys to eventually become activated into 1,25 dihydro (activated D-3)

Question 34

Melanocytes

Answer 34

Are neural crest derived cells that primary function is to produce melanin that is contained in melanosomes to be secreted to neighboring keratinocytes as needed - Are located in the stratum basale of the epidermis Function of melanin = provide color to skin/hair/eyes and photoprotection against ionizing radiation - contains eumelains and pheomelanins

Question 35

How is melanin produced

Answer 35

Oxidation of tyrosine AAs into 3,4 dihydroxyphenylalanine (DOPA) DOPA is then transformed into eumelanin **albunism occurs when melanocytes either cant produce melanin or are too low in numbers to keep up**

Question 36

Griscelli syndrome

Answer 36

Mutation in the myosin Va gene | - produces silvery hair and partial albinism and immunodeficiencies

Question 37

Glucocorticoid function on skin

Answer 37

Loosens intercellular connections of epidermis and results in decreased effectiveness of the barrier

Question 38

Thyroid hormone function on skin

Answer 38

maintains normal blood flow to the sub papillary plexus of the skin

Question 39

Sex hormones function on skin

Answer 39

Stimulates epidermal cell division and increases thickness of the epidermal layer Also accelerates wound repair Increases number of dendritic cells protection against cancer cells and pathogens

Question 40

Growth factors effects on the epidermis

Answer 40

Stimulate cell growth and cell division in both the dermis and epidermis

Question 41

Epidermal growth factor (EGF)

Answer 41

Promotes cell division in the deeper epidermal layers, keratin production, epidermal repair and secretion by epithelial glands and salivary glands

Question 42

Growth hormone effects on the skin

Answer 42

Stimulates fibroblast activity and collagen synthesis Stimulates basal cell division Thickens epidermis Promotes wound repair

Question 43

4 phases of skin regeneration

Answer 43

1) inflammatory phase - bleeding and injury occurs at the site of injury which triggers substance P to be released from damaged cells - substance P casues degranulation of mast cells and inflammation response 2) migratory phase - begins scab formation and galati on tissue formation - patrolling macrophages remove debris and pathogens - rapid cell division and migration along wound edges to replace missing cells occurs 3) proliferation phase - deeper portions of the scab dissolve and fibroblasts produce new collagen fibers and ground substance 4) scarring phase - formation of healed scar tissue

Question 44

4 stages of damage recognition and repair mechanism

Answer 44

1) coagulation - formation of the fibrin-platlet clot 2) inflammation - leukocyte recruitment 3) proliferation - neovascularization and formation of granulomation tissue 4) remodeling and resolution