Integumentary High-Yield Biomedical Sciences Flashcards

Biomedical Sciences, Sourced from emma_dip on Quizlet

Describe the embryological development of the epidermis

-derived from single layer of surface ectoderm cells

-divide in second month to form periderm layer (epitrichium)

-then desquamate in 1st half of prenatal life to form vernix caseosa

-neural crest cells invade epidermis to form melanocytes (hair and skin pigmentation)

*4 layers formed by month 4: basal/germinative layer, spinous layer, granular and horny layer

Describe the embryological development of the dermis

-derived from mesenchyme via 3 sites:

1. lateral plate mesoderm: dermis of limbs, body wall

2. paraxial mesoderm: back

3. neural crest cells: neck, face

*in 3-4 months, dermis forms papillary structures (dermal papillae) containing meissner corpuscles/tactile sensory receptors

Describe the embryological development of the hair

-hair follicles from cells of stratum basale (start as epidermal proliferations) and penetrate into dermis (aka. hair bud)

-hair bud invaginates and forms papillae at the end

-papillae fill with mesoderm (vessels, nerves develop)

-hair shaft forms from keratinization and peripheral cells form hair sheath

-surrounding mesenchyme forms dermal root sheath and attach arrector pili muscles

-sebaceous glands form from mesoderm which secretes sebum

Describe the embryological development of the nails

3rd month

-nail fields form at ends of digits

-Epidermis differentiates into nails and reach the tips by 9th month

Describe the types of sweat glands and the embryological development of each

1. Eccrine glands

-coiled tubular sweat glands

-walls are simple or stratified cuboidal epithelium with dense cytoplasm

-found in thick and thin skin of dermis over most of the body (not lips, ears, clit or penis)

-germinative layer buds grow into dermis, terminal part coils and forms secretory part of glands

2. Apocrine glands

-bigger and fewer than eccrine

-secretions contain more lipids and proteins (bacteria feed off secretions)

-develop in puberty over hairy parts (armpits and genitals)

-epidermal buds that produce hair follicles

3. Mammary glands

-modified sweat glands

4. Ceruminous glands

-earwax

What (in the derm system) does the ectoderm give rise to?

Skin

What (in the derm system) do neural crest cells give rise to?

Melanocytes

Describe tight junctions

Zonula occludens

-prevent/regulate paracellular movement of solutes

-composed of claudins and occludins

Describe adherens junctions

Belt desmosome, zonula adherens

-forms 'belt' connecting actin cytoskeletons of adjacent cells with CADherins

-loss of E-cadherin promotes metastasis

CADherins = Ca2+ dependent ADhesion proteins

Describe desmosomes

Spot desmosome, macula adherens

-bind cells together

-structural support via intermediate filament interactions

-has CADherins (Ca2+ dependent ADhesion proteins)

What do autoantibodies to desmoglein 1 and/or 3 cause?

pemphigus vulgaris

Describe gap junctions

-channel proteins called connexons

-permit electrical and chemical communication between cells

Describe hemidesmosomes

-connects keratin in basal cells to underlying basement membrane

-have INTEGRIns -> membrane proteins that maintain INTEGRIty of basolateral membrane via binding to collagen, laminin and fibronectin in basement membrane

What do autoantibodies to hemidesmosomes cause?

bullous pemphigoid

(hemidesmosomes are down 'bullow')

Describe the 3 layers of skin

OUTER: Epidermis

-5 layers made of keratinocytes

-keratinocytes contain cholesterol precursors to make vitamin D via UVB light

-keratinocytes also filled with keratin protein (protective from damage)

-make and secrete glycolipids

-contains melanin

MIDDLE: Dermis

-2 layers: thin/papillary and reticular layer

-temperature regulation

-contain oil and sweat glands, lymph, hair follicles and nerves (pacinian corpuscles)

INNER: Subcutaneous/Hypodermis

-attach to deeper muscles

-contain adipocytes

-fat, fibroblasts, macrophages, blood vessels, nerves, lymph

Describe the 5 layers of the epidermis

“Come Let’s Get SunBurned”

(stratified squamous epithelium)

1. Stratum Corneum

-outermost layer

-20-30 dead squamous keratinocyte layers glued with glycolipids

-dead cells secrete defensins (natural abx)

-no nucleus or organelles

-filled with keratin filaments

2. Stratum Lucidum

-2-3 dead keratinocyte layer

-translucent, dead keratinocytes secreted from lamellar granules

-no nucleus or organelles

-only in thick skin (palms/soles of food)

*thick skin is lucky/lucidum to get an extra layer*

3. Stratum Granulosum

-3-5 flattened keratinocytes layer undergoing keratinization

-keratinocytes produce keratohyalin (form keratonin) and lamellar granules (stick to outer cell surfaces and form 'glue' between cells) which aggregate and cross-link

-keratinocytes then flatten out and die

-dead keratinocytes move to Lucidum layer

4. Stratum Spinosum

-8-10 keratinocyte layers

-synthesize keratin and other proteins

-mature keratinocytes that have lost the ability to divide move from Basale to Spinosum

-containdendritic cells and tiny spine like proteins for cell adherence

5. Stratum Basale

-bottom layer

-keratinocytes and melanocytes

-single layer cuboidal or columnar germ cells (stem cells)

-attached to basement membrane

-increased mitotic activity in these cells = continuous dividing and producing new keratinocytes

-produce ALL cells that migrate to surface (pushed up by new cells)

-have cholesterol precursors for Vitamin D production through UVB light

-melanocytes secrete melanin stimulated by UVB light, melanosomes scatter UVB light

-melanin stored in melanosomes

Describe the 2 layers of the dermis

Middle layer

-divided into:

1. papillary layer (THIN)

-made of fibroblasts (produce collagen) arranged in papillae = makes fingerprints

-contains free nerve endings, meissner's corpuscles and macrophages

-contain blood vessels that dilate when hot = blood to surface for heat loss

-contract when cold = shunt blood away to prevent heat loss

2. reticular layer [THICK]

-Made of fibroblasts (produce elastin for flexibility) with scattered macrophages

-fibroblasts secrete elastin which increases skin flexibility

-collagen packed more tightly for support

-contains oil glands, sweat glands, lymphatics, BVs, hair follicles, macrophages

-regulates temperature

-contains pacinian corpuscles for proprioception and vibration

Describe the hypodermis

Subcutaneous inner layer

-contains adipocytes (fat stores), fibroblasts, macrophages, BVs, nerves, lymphatics

-insulates deeper tissues

-provides padding

-anchors skin to muscles underneath with connective tissue (collagen)

Describe the micro anatomy of hair follicles

Hair shaft

-dead keratinocytes and inner root sheath (surrounds hair shaft in hair follicle)

-outer layer follicle (henles layer) = simple cuboidal cells (single)

-inner layer follicle (huxleys layer) = double layer of flat cells

-hair strand sits in follicle (epidermal tissue) which dips into dermis (bulb)

Root

Bulb

-hair matrix containing follicular keratinocytes {hard keratin} and melanocytces

-bulb made of specialized basal epithelial cells (keratinocytes)

-blood supplied by papillae

Describe the micro anatomy of the dermis around hair follicles

-sebaceous glands (oil glands) = secretes sebum when arrector pilli contract

-arrector pili muscle contracts, pulls hair up when cold

-apocrine glands nerve receptors stimulated when hair shaft is moved

Why does grey hair occur with age?

decrease in melanin

Describe nail anatomy

1. Eponychium

-proximal

-lunula = white crescent part of nail near eponychium

-nail fold gives rise to cuticle (dead skin keratinocytes) -> so pathogens cant get in

2. Nail matrix

-special epidermal tissue that dips into dermis contains modified keratinocytes that are young and undergo keratinization

-nail plate = contains dead keratinocytes

What are eccrine glands?

-merocrine or sweat/salivary glands

-found everwhere except lips, ears, clitoris, glans of penis

-in dermis (reticular)

-epithelial derivative

What is sweat composed of?

-hypotonic (relative to blood)

-contains water, electrolytes, dermicidin, vitamin C

-contains dermicidin to destroy bacteria

-increased by SNS activity (working out, fear, anxiety, etc)

-cools body by evaporation

What are apocrine glands?

-modified sweat glands

-found in armpits, genitals

-become active during puberty

-epithelial derivative in dermis layer (reticular) contributes to body odour

What are holocrine glands?

-aka sebaceous glands

-mesoderm derivative

-associated with hair follicles

"when you have acne you don't want to say "holo" to anyone"

Where are holocrine, apocine and eccrine glands found in the body?

-Holocrine and Apocrine glands are associated with hair follicles,

-Eccrine are found everywhere (some exceptions)

What receptors regulate temperature?

Peripheral = cutaneous thermoreceptors

Central = spinal cord, visceral thermoreceptors, hypothalamic

Describe the process of temperature regulation via the skin

1. Hypothalamus receives input from skin and spinal thermoreceptors

-somatosensory

-activates warm and cold sensing neurons

-perceives thermal change

2. Hypothalamus preoptic area

Receives somatosensory input and responds:

-heat production and retention protocol if -20 degrees C due to cold neurons activated

-heat loss protocol if external temp +40 C and warm sensing neurons activated

3. Temperature regulation

Heat loss mechanisms:

-vasodilation

-sweating

-decreased metabolic rate

-reduced activity (ie. reduce appetite)

Heat conservation mechanisms:

-vasoconstriction

-piloerection (goosebumps)

-increased metabolic rate

-increase activity

-shivering thermogenesis

-brown adipose tissue [BAT] = thermogenesis

Describe the process of fever production

1. Exogenous pyrogens (toxins/organisms)

- activate endogenous pyrogens

-IL-1, IL-6, TNF, IFN

2. Endogenous pyrogens arrive at OVLT

-produce prostaglandin E 2 via COX enzyme

3. Leaky blood brain barrier allows PGE2 to travel to preoptic area of hypothalamus

-elevate set point and initiate heat conservation strategy

-increases cold sensing neuron activity and decreases heat sensing neuron activity = elevate internal temperature

Elevating internal temperature =

-enhance immune response

-impair viral/bacterial replication

-decrease blood glucose levels

-initiate acute phase protein production from liver (bind divalent cations/iron, assist immune system, ex. CRP)

What is hyperthermia?

-over 42 degrees C

-causes cytotoxicity, protein denaturation, impaired DNA synthesis, end organ failure, neuron impairment

At what temperature is thermoregulatino lost?

at 45 C

What is pyrexia?

Fever

-change in set point hypothalamus to increase body temp

What is hyperpyrexia?

Extreme elevation due to underlying disease/disorder (ie. subarachnoid hemorrhage)

What type of skin cells are found in the epidermis?

ALL are Keratinocytes attached via desmosomes

-except for germ cells in basalis layer

Distinguish between thin and thick skin

Thin

-1-2mm

-thin

-has hair follicles and sebaceous glands

Thick

->5mm

-outer layers

-palms and soles

-no hair follicles, sebaceous glands

-has sweat glands

Describe hos the dermis and epidermis layers are connected

-via dermal papillae with epidermal ridges (irregular junction - papillary layer)

-papillary layer improves adhesion

-pap layer thinner in thin skin

Which corpuscles are found in dermal papillae?

Meissners corpuscles

-perpendicular to surface

-mechanoreceptors that sense physical pressure/movement and light touch, low frequency vibration

What layer is found under the papillary layer?

Reticular layer

-thicker

-lots of dense, irregular connective tissue

-contains sweat glands, pacinian corpuscles

(in thin skin - also hair follicles, sebaceousglands and arrector pilli)

Describe pacinian corpuscles

Pressure sensors located deep in the skin

-shaped like an onion, composed of 20-60 concentric lamellae (modified schwann cells with central inner, unmyelinated pulp and outer connective tissue cap)

-when membranes becomes distorted nerve endings become polarized

-sense coarse touch, pressure, high frequency vibrations

What brings nutrients to hair?

dermal papillae at hair bulb brings nutrients to growing basal cells

What glands are found next to hair follicles?

Sebaceous glands

-cytoplasm filled with fat which drain into hair follicles

-found everywhere except palms, soles, lips

-sebum released when arrector pili contract

-androgens increase sebum release (acne, folliculitis)

-lots of glands in face- why acne common here

What is the difference between soft and hard keratin?

Soft

-present in skin

Hard (more dense)

-hair

-nails

Describe keratinization in hair cells

-keratinocytes filled with hard keratin

-organelles flatten out

-keratinocytes die and turn into compact, flat cells

-dead cellsget pushed up into hair follicles

*keratinocytes in bulb only replicated a set number of times, then will stop and fall out = baldness

Descibe the 3 types of tissue regeneration

1. Labile

-places with stem cells; healh very well

-skin

-connective tissue

-small and large intestine

2. Stable

-no stem cells; use mature differentiated cells that divide or regenerate (hyperplasia)

-liver

3. Permanent

-weak regeneration bc no stem cells so cannot replicate

-injury replaced by scar tissue = loss of function

-skeletal muscle

-cartilage

-neurons

-cardiac tissue

Describe the 3 types of skin healing

1. Primary intention

-wound edges come together

-stem cells in epidermis are close together so can rejoin

2. Secondary intention

-edges too far to connect

-wound replaced by connective tissue that grows from base up (inside out)

-tooth extraction, severe burns

3. Tertiary intention

-wound too big

-cleaned, left open and observed

-left open d/t high potential for bacterial contamination

-if closed too early will cause abscess or walled off infection

Describe the 5 steps of wound healing

1. Hemostasis

-blood clot forms at site

-affected blood vessels constrict

-platelet plug and fibrin form

2. Inflammation

-chemokines and cytokines released

-blood vessel dilation and leakage

-immune cells clear foreign debris, digest damages and dead cells, destroy microbes

-blood clot and dead macrophages form a scab

3. Epitheliazation (migration)

-takes 48 hours

-basal cells (stem cells) in epidermis proliferate and replace lost/damaged cells

-ends when epidermal layer rejuvenated

-skin still weak bc dermal layer below hasnt rejuvenated yet

4. Fibroplasia

-wound stronger and damage resistant

-fibroblasts proliferate and secrete collagen (fibroplasia)

-collagen stimulates blood vessel growth

-collagen groups to form fibrils and then collagen bundles (high tensile strength, extracellular scaffolding)

-fibroblasts also produce glycoproteins and sugars that make up ground substance (glue) between cells and wall

*ultimately produces granulation tissue (red tissue under scab) in dermal layer

5. Maturation

-wound gets more support

a) collagen cross linking via covalent bonds

-enhances tensile strength

b) collagen remodeling

-fibroblasts degrade subpar collagen

c) contraction

-myofibroblasts produce contractile proteins in cell

-contractile proteins attach to transmembrane proteins which attach to proteins in interstitial space

-when proteins contract, edges of wound pulled together

d) repigmentation

-melanocytes proliferate and restore normal colour

What factors prevent wounds from healing?

Capillary narrowing from:

-disease like diabetes

-prolonged compression

-atherosclerosis

-infection (bc compete for O2, cause damage and inflammation)

Decreased blood flow results in fewer immune cells in area resulting in tissue necrosis

Edema can also disrupt fibroblast activity, collagen deposition and cross linking

Describe the process of vitamin D generation via UV light

IN EPIDERMIS

1. 7-dehydrocholesterol

-product produced in cholesterol synthesis

-can go on to become cholesterol or vitamin D

2. Pre-vitamin D3

-from exposure to UV light (290-315nm)

3. Cholecalciferol (inactive vitamin D)

-from any heat source

IN LIVER

4. 25-hydroxycholecalciferol (calcidiol)

-via p450 enzyme 25-hydroxylase

IN KIDNEY

5. 1,25-dihydroxycholecalciferol (calcitriol)

-via p450 enzyme 1-hydroxylase

-ACTIVE VITAMIN D

1,25-dihydroxy binds to vitamin D receptor in cell cytoplasm which then travels to nucleus and binds to VDRE in DNA to produce proteins which result in cellular and systemic effects

How is collagen formed?

NUCLEUS

1. Transcription of collagen gene

INTRACELLULAR

2. translation to pre-procollagen

-glycine and 2 random AAs (usually proline and lysine)

3. alpha chain synthesis via post translational modification

4. procollagen assembly via hydroxylation

-galactosyltransferase or glucosyltransferase add glucose or galactose to hydroxyl groups

5. stable triple helix formation

-3 type 5 alpha 1 chains OR

- 2 type 5 alpha 1 chains and 1 type 5 alpha 2 chain

EXTRACELLULAR

6. proteolytic processing

-cleavage of propeptides via collagen peptidases

7. tropocollagen (mature)

-fibril formation via self assembly

8. collagen fiber formed via cross linking by lysyl oxidase

What genes are responsible for collagen synthesis?

COL __ __

first blank = type of collagen

second black = pro alpha chain

Differentiate 5 types of collagen

1. Type 1

-skin, tendons, organs, bones

2. Type 2

-cartilage (joints)

3. Type 3

-reticular fibers

-supporting mesh for soft organs

4. Type 4

-basal lamina (epithelial cells)

5. Type 5

-cell surfaces, hair and placenta

-also places with type 1