integumentary system

What are keratinocytes?

Produces protein - keratin,

• helps waterproof

• Protects from light, heat, microbes

Desmosomes anchor keratinocytes to each other

What are melanocytes?

Produce dark pigment - melanin

• Can migrate to adjoining keratinocytes → forms a protection over nucleus

• Melanin shields genetic material from UV light

What are langerhans cells?

Arise from bone marrow and migrate to epidermis

• Plays a role in immune response

What are merkel cells?

Stem cells (germinative cells) precursors of keratinocytes

• Located in deepest layer of epidermis

How many layers does the epidermis mostly assist of? What about in the palms and soles?

4 layers in most places, 5 in palms and soles

What is stratum basale or germinativum?

Cells undergo continuous cell division (stem cells) and produce all other lays

• contains tactile discs

• Sensitive to touch

What is stratum spinosum?

Contains keratinocytes and projections of the melanocytes

• keratinocytes lose nucleus → degenerate → die

What is stratum granulosum?

Cells contain precursor of keratin - keratohyalin

What is stratum lucidum?

Contains a substance - ELEIDIN that can be converted to keratin

• only in palms, fingertips, and soles

What is stratum corneum?

Cells constantly shed and replaced by cells in deeper strata

• completely filled with keratin

• Form effective barrier of skin

What is thickening of epidermis?

Callus

• Result from excessive keratin production - hyperkeratosis

What is keratinization?

Replacement of cell contents with keratin

• occurs as cells move to skin surface over 2-4 weeks

• Cytoplasm, nucleus, organelles disappear and cells die

What is epidermal growth factor - EGF?

Protein that stimulates growth of epithelial/epidermal cells during tissue development, repair and renewable

What are the layers of dermis?

• Papillary layer: superficial layer of connective tissue containing fine elastic fibers

• Reticular layer: deeper layer of irregular connective tissue containing collagen/elastic fibers, hair follicles, nerves, pacinian corpsucles, sebaceous glands, ducts of sudoriferous glands

What makes up the papillary layer?

• Dermal papillae: fingerlike projections that increase its area

  • Secretions from this leaves fingerprints

• Epidermal ridges: reflect contours of underlying dermal papillae

  • Increase friction for better grasping ability

  • Basis for fingerprints and footprints

  • Ridge pattern is GENETICALLY DETERMINED and different for each individual

What is sensation provided by?

• Lamellated or Pacinian corpuscles

• Nerve endings

• Merkel cells and Meissener’s corpuscle

Describe melanin.

• Produced by melanocytes in epidermis

• Synthesized from tyrosine (amino acid) in melanosome (organelle) by tyrosinase (enzyme)

• Exposure to UV light → increase activity tyrosinase → more melanin to protect skin

• Tan: defensive mechanism against damaging UV rays → disappears when excess melanin is lost in dying keratinocytes

• Albinism: LACK TYROSINASE → cant make melanin

• Freckles: patches of concentrated melanin

What is carotene?

Yellowish orange pigment that is precursor of vitamin A

• antioxidant: inactivates toxic free radicals

What scars form during deep wound healing?

• Hyperthrophic scar: raised scar tissue, elevated above epidermis, within boundaries of wound

• keloid scar: extends beyond wound boundaries

What are the 4 phases of deep wound healing?

1. Inflammatory phase: blood clot at wound, vasodilation, increased permeability of blood vessels deliver phagocytes, mast cells, fibroblasts

2. Migratory phase: epithelial cells below scab close wound, fibroblasts make scar tissue, blood vessels grow - GRANULATION TISSUE

3. Proliferative phase: events of migratory phase increase

4. Maturation phase: scan disappears, falls off, epidermis back to normal

Describe different skin grafts.

1. Autograft: from same individual

2. Isograft: identical tein

3. Autologous: grown in labratory

4. Homograft: from another person (cadaver)

5. Heterograft: from animal - NOT HUMAN

What are hair disorders?

1. Hirsutism: excessive hair in females/pre-pubertal males from excessive androgens (from ovaries/adrenal glands)

2. Male Pattern Baldness: genetically predisposed males - androgens INHIBIT hair growth

   1. Give Rogaine: vasodilator that brings blood to skull → stimulates hair growth

What are the different types of cancer?

1. Carcinomas: epithelial cell cancer

2. Melanomas: cancer of melanocytes - EASILY MESTASIZES

3. Sarcoma: cancers of muscle or connective tissue- more rare

4. Leukemia: white blood cells

5. Lymphoma: lymphatic tissue

What are forms of SKIN cancer?

1. Basal cell carcinoma: from epidermis - DONT METASTASIZE

2. Squamous cell carcinoma: from epidermis - DOES METASTASIZE

3. Malignant melanoma: from melanocytes - metastasize intensive and kills within months of diagnosis

What are the different types of tumors?

1. Benign tumor: stays there → doesnt do anything

2. Malignant tumors: cancer

   1. Hyperplasia: increase in number - continues dividing

   2. Metastasis: spread of malignant cells by bloodstream and spreads throughout body

What are stages of metastasis?

Invasion, penetration, escape

What is sebum made of?

Fats, cholesterol, proteins, inorganic salts

What are other skin growths?

1. Wart: non-cancerous mass - caused by PAPILLOMAVIRUS

2. Hemangioma: localized benign tumor of skin from birth

3. Nevus: round pigmented area present from birth

What is german measles?

Begins respiratory system - caused by rubella virus - CONSISTS OF RASH AND RED SPOTS IN SKIN

• highly contagious disease

What is impetigo?

Superficial skin infection caused by staphylococci