Integumentary System - Anatomy + Physiology

Integumentary system organs

Skin (thick and thin)

Accessory: hair, nails, glands

Integumentary system function

Cover and protect body. Protects from injury, infection and UV radiation

3 layers of skin

Epidermis, dermis, hypodermic (subcutaenous)

Epidermis

Top/superficial layer of skin. Made of stratified squamous ET. 4/5 layers (corneum, lucidum, granulosum, spinosum, basale/germinativum)

Stratum basale

Deepest/bottom layer. Closest to dermis. 1st layer of cell life cycle. Single (ish) layer of more cuboidal shapes. Highly mitotic. STEM cells, pumps out skin cells (keratinocytes). As they grow and mature, they move up the layers

Stratum spinosum

8-10 layers. Appears spiny/spiky. So so so many desmosomes. Cells tightly knit together. Makes keratin

Stratum granulosum

Grainy (packed full of keratin granules). Holding keratin. 3-5 layers

Stratum corneum

Dead cells (keratin). Keratinocytes that have done their job. Constantly replaced and sloughing off. Very flat. 15-30 layers

Stratum lucidum

Only in thick skin (palms and soles). Produces eleiden - adds a waterproofing function to thick skin. Can withstand wear and tear. Only a few layers thick. Why thick skin is lighter in color

Eleiden

Clear, protein, lipid rich. Found in the stratum lucidum of thick skin

Stem cells

Make keratinocytes. Basale layer of epidermis.

Melanocytes

Melanin cells. Found in basale layer. Produces melanin. Protects skin from UV radiation (gives keratinocytes little melanin umbrellas to protect themselves). We all have the same amount, but they produce different amounts of melanin

Melanin

Dark brown pigment. Cause of skin and hair color

Merkyl (tactile) cells

Provides tactile function. Touch receptors. Found in the basale layer

Langerhan cells

Dendritic cells. Macrophages (cellular eaters). Engulfs foreign substances. Found in the granulosum. Antigen presenting cells (APCs)

Keratinocytes

Produce keratin (a tough, insoluble fibrous structural protein that acts as the primary component of hair, nails, and the epidermis)

Albinism

Very little melanin being produced. Prone to UV damage. Inherited autosomal recessive condition

Dermis

Thickest layer. Papillary layer (loose areolar CT) and reticular layers (dense irregular CT). Houses touch receptors and accessories

Papillary layer

Loose areolar CT. About 20% of dermis. Contains meissner’s corpuscles + fibroblasts

Meissner’s corpuscle

Touch receptor for pressure/touch

Reticular layer

Much larger than papillary. Dense irregular CT. Needs to withstand stress from multiple directions. About 80% of dermis. Pacinian corpuscles + fibroblasts

Types of sweat glands

Apocrine and eccrine

Apocrine sweat glands

Armpits and genital areas. Scent glands

Eccrine sweat glands

Regular sweat glands. All over body, merocrine glands

Friction ridges/dermal ridges

Thick skin, dermal papillae, fingerprints, changes shape of epidermis. Improves grip and sensitivity

Hypodermis

Connects dermis to underlying muscle/bone. Mostly adipose tissue. Lots of blood vessels. Major site of fat storage (subcutaneous fat)

Hair

Derived from epidermis. Made of keratinocytes moving up from the shaft, strand of dead keratinocytes, color is derived from the amount melanin being produced. Texture is derived from the shape of the hair shaft as it goes through epidermis

Arrector pili muscle

Attached directly to hair shaft. Causes goose bumps. Involuntary. Pulls hair up and makes it stand when contracted. Help with warmth and protection

Sebaceous glands

Usually associated with hair. Oil glands. Produce sebum for lubrication

Nails

Extension of epidermis, protects distal dorsal digits. Eponychium, lunula, made are keratin, glands, nail bed

Eponychium

Cuticle

Lunula

White circle on nail

Nail body

Outer nail portion

Nail bed

Underlying nail stuff

Sebum

Oil-like substance produced by sebaceous glands

Functions

Cover and protect, vitamin D synthesis, temp regulation, sensation (touch receptors)

Cover and protect function

Layer the body, protect from injury, infection, harmful UV, and dehydration. 1st line of defense

Vitamin D synthesis

Produced by cholesterol, sun triggers skin to produce. Necessary to absorb calcium and phosphorous. Vital for immune system

Rickets

Childhood vitamin D deficiency. Soft, bendy bones

Temp regulation

Regulates body temp via blood. Flow changes and sweating. Stores around 20% of blood in skin

Sensation

Touch receptors

Homeostatic imbalances

Excretion and absorption. Fat soluble vitamins can go through skin, excrete salt, ammonia

Bedsores

Pressure ulcers. Develop when constant pressure cuts off blood supply, causing tissue death (stage 1 is epidermis, up to stage 4 which is down to muscle and bone). Common in elderly people and people with spinal cord injuries

Basal cell carcinoma

Starts in stratum basale. Common. Low metastatic rate (least dangerous), shiny red domed nodules

Squamous cell carcinoma

Originates in stratum spinosum. Quick to grow and metastasize (scaly patches of skin), less common, more dangerous

Melanoma

Melanocytes, high metastatic rate, very dangerous, black patches of skin

Burns

Tissue damage via heat, electricity, radiation, chemicals: 1st, 2nd, 3rd, 4th degree

1st degree burn

Only affects epidermis; red, painful

2nd degree burn

Into dermis; blistering, more serious

3rd degree burn

Entire death of dermis; little to no pain

4th degree burn

Burn damage down to muscle

Dermal papillae

small, nipple-shaped, vascular, and nerve-filled connective tissue projections that extend from the dermis into the epidermis, enhancing nutrient exchange and skin adhesion

Desmosome

a specialized, spot-like cell junction that anchors adjacent cells together, providing high mechanical strength and structural integrity to tissues

Metastasis

the biological process where cancer cells break away from a primary tumor, travel through the bloodstream or lymphatic system, and form new, secondary tumors in other organs or tissues

Hair follicle

a tunnel-shaped, regenerating, mini-organ located in the epidermis and dermis that produces and anchors a hair strand

Hair matrix

a layer of highly active, proliferating epithelial cells located at the base of the hair follicle within the hair bulb

Hair root

the living, germinative portion of a hair strand located below the skin's surface, anchored within the hair follicle in the dermis

Hair shaft

the visible, non-living, and keratinized portion of a hair that extends above the surface of the epidermis

Hyponychium

the thickened layer of epidermis (skin) located immediately beneath the free edge of the nail plate, marking the transition between the nail bed and the distal fingertip

Keratohyalin

insoluble, electron-dense cytoplasmic inclusions found primarily in the stratum granulosum of the epidermis, composed of proteins like profilaggrin, loricrin, and trichohyalin

Pilus

thin, hairlike, proteinaceous appendages found on the surface of many bacteria, primarily gram-negative species

Sudoriferous glands/sweat glands

small, coiled tubular exocrine glands located in the dermis layer of the skin that produce sweat for thermoregulation, waste removal, and skin hydration. Eccrine and apocrine