Integumentary System & Skin

• The theme is to live by the 5 C's: competence, character, committment, collaboration and creativity.
• These characteristics can be achieved through academic rigor, growth mindset, and grit.
• Body temperature must be controlled.
• The difference between body heat and temperature must be understood.
• The function of skin in temperature control must be understood.

Integumentary System Basics

• The integumentary system is the skin.
• The skin, along with its appendages, composes the integumentary system
• Deep to the skin lies a fatty layer called the hypodermis.
• The skin has two distinct regions, the epidermis and the dermis.

Skin Facts

• Skin is the largest organ with an approximate surface area of 25 sq ft.
• Each square inch of skin contains 20 feet of blood vessels and an average of 32 million bacteria.
• A person regrows a new skin approximately every 27 days.
• Fingernails and toenails take 6 months to grow from base to tip.
• The average human scalp has 100,000 hairs.
• Humans lose an average of 40-100 strands of hair a day.

Functions of Skin

• The skin provides protection, cushioning, insulation, and waterproofing.
• The skin protects from chemicals, heat, cold, and bacteria.
• The skin screens ultraviolet light and synthesizes vitamin D with UV light.
• The skin regulates body heat, also known as thermoregulation, and prevents unnecessary water loss.
• The skin facilitates sensory reception through nerve endings.

Epidermis

• The epidermis contains three types of cells: keratinocytes, melanocytes, and merkel cells.
• Keratinocytes are the deepest cells which produce keratin.

Keratin

• Keratin is a touch fibrous protein.
• Melanocytes make dark skin pigment called melanin.
• Merkel cells are associated with sensory nerve endings.
• The layers of the epidermis run from deep to superificial.
• The stratum basale or germinativum is a single row of cells attached to the dermis and comprise of the youngest cells.
• The stratum spinosum, "spinyness" is artifactual, and tonofilaments resist tension through bundles of protein.
• The stratum granulosum contains layers of flattened keratinocytes producing keratin, which hair and nails are made of.
• The stratum corneum is the horny layer of dead cells and many layers thick.

Dermis

• The dermis is strong, flexible connective tissue called the "hide".
• The dermis contains fibroblasts, macrophages, mast cells, and WBCs.
• The dermis contains collagen, elastic, and reticular fiber types, plus a rich supply of nerves and vessels.
• The dermis plays a critical role in temperature regulation through its vessels and consists of two layers.
• The Papillary layer comprises of areolar connective tissue, including dermal papillae.
• The Reticular layer is a "reticulum", or network, of both collagen and reticular fibers.

Hypodermis

• The hypodermis is below the skin. The Greek word "Hypodermis" translates to below the skin.
• Subcutaneous translates to below the skin, from Latin.
• The hypodermis is also called the "superficial fascia".
• Fascia, from Latin, is a sheet of connected tissue in anatomy.
• The hypodermis is fatty tissue which stores fat and anchors the skin. Accumulation patterns differ between males and females.

Skin Color

• Three skin pigments are responsible for skin color: melanin, carotene, and hemoglobin.
• Melanin is most important.
• Carotene comes from carrots and yellow veggies.
• Hemoglobin provides the pink color of light skin.
• Melanin in granules passes from melanocytes, and all races have the same number, to keratinocytes in stratum basale.
• Melanin is then digested by lysosomes, resulting in variations in color, also contributing to protection from UV light vs vitamin D.

Skin Appendages

• Skin appendages originate from the epidermis but extend into the dermis.
• Skin appendages include hair and hair follicles, sebaceous (oil) glands, sweat glands, and nails.

Nails

• Nails are made of hard keratin, and correspond to hooves and claws.
• Nails grow from the nail matrix.

Hair and Hair Follicles

• Hair and hair follicles come from the epidermis and dermis.
• Except fot the palms, soles, nipples and parts of genitalia: hair covers the entire body
• Functions of hair include warmth, although less so in humans, sensitivity to light touch and protection of the scalp.
• Hair parts include root, which is imbedded in the skin, and the shaft, which projects above the skin.

Hair Structure

• Hair makeup contains hard keratin.
• Hair has three concentric layers: Medulla (core), cortex (surrounds medulla), and cuticle (single layers overlapping).

Thermoregulation

• Thermoregulation in the integumentary system has several components working to maintain homeostasis.
• Sweat glands are found on the entire skin surface except nipples and parts of the external genitalia.
• Sweat glands prevent overheating, and can produce from 500 cc to 12 liters a day of mostly water.
• Humans are the most efficient mammals when it comes to these glands, and they are produced in response to both heat and stress.
• Insulation can consist of layers of fat, fur, or feathers to prevent heat loss.

Temperature Regulation

• Shivering occurs when you are cold, raises core body temperature
• Sweating occurs when you are hot, lowers core body temperature
• Hypothermia is a medical emergency which occurs when your body loses heat faster than it can produce it, resulting in dangerously low body temperatures.
• Normal body temperature is around 98.6 F (37C).
• Hypothermia occurs when body temperature drops below 95 F (35C).

Thermoregulation and Skin Parts

• Hair stands upright to keep a layer of warm air next to the skin when cold (convection).
• Hair erector muscles contract to cause the hair to stand upright in order to reduce heat loss when cold.
• Sweat evaporates from the sweat gland in order to increase heat loss from the body when warm.
• Nerve endings sense changes in the surface temperature of the skin and send the information to the brain along a sensory neuron.

Vasodilation and Vasoconstriction

• Vasodilation widens to allow more blood to flow, which increases heat loss from the body when hot.
• Vasoconstriction narrows to allow less blood to flow, which reduces heat loss from the body when cold.

Skin Problems

• A rash is the irritation and reddening of the skin without itchiness.
• Dermatitis inflammation of the skin, characterized by hot and red skin.
• Eczema inflammation of the skin includes itchy rashes.
• Psoriasis contains silver and scaly skin rashes to the scalp.
• Dandruff is a scaly condition of the scalp.
• Acne occurs when hair follicles are clogged with dead skin cells and oil from the skin.
• Cellulitis occurs when inflammation of the dermis and subcutaneous tissue is due to infection and features a red warm, often painful rash.
• A skin abscess is a boil or furuncle infection creating a collection of pus under the skin.
• Warts occur when a virus infects the skin, growing excessively.
• Melanoma is skin cancer caused from sun damage.
• Carcinoma is skin cancer ulcer that will not heal, or an abnormal growth, due to sun exposure.
• Herpes is the periodic blister or skin irritation around lips, tonsils and genitals.
• Shingles (Herpes Zoster) is a painful rash on one side of the body caused by the chickenpox virus.
• Scables is an intensely itchy rash in the web of the fingers, wrist, elbow, and buttocks.
• Ringworm is a fungal infection of the skin called "tinea" in ring shape but not caused by a worm.