HHP3115 Chapter 5 Integumentary System Notes PDF

Chapter 5: Integumentary System The Integumentary system includes… - Skin (what we’ll focus on today) - Sweat/oil glands - Hair - Nails Skin: our largest ORGAN - Accounts for 7% of body weight (not on test) - Varies in thickness, from 1.5-4.4 mm (not on test) o Thick skin is fou...

Chapter 5: Integumentary System The Integumentary system includes… - Skin (what we’ll focus on today) - Sweat/oil glands - Hair - Nails Skin: our largest ORGAN - Accounts for 7% of body weight (not on test) - Varies in thickness, from 1.5-4.4 mm (not on test) o Thick skin is found in palms/soles (have an extra layer o Thin skin is found everywhere else - Divided into two distinct layers o Epidermis (epithelial tissue) – very thin o Dermis (connective tissue) – majority of our skin Hypodermis: lies deep to the dermis - Structurally and functionally related to skin, but not technically part of it - Largely fat Function of the skin: - Cushions and insulates deeper organs - Protects body from bumps/scrapes/cuts - Protects body from chemicals/heat/cold - Mini-excretory system (through sweat) - Vitamin D production (required for calcium in bones) - Contains sensory receptors associated with nerve endings Four main cell types of the skin: - Keratinocytes: make up majority of epidermis o Produce keratin (a tough fibrous protein) o Arise from the deepest layer of the epidermis  Die over the course of ~35-45 days as they move outwards, and eventually fall off on the skin’s surface o Produce antibodies and enzymes, fighting off microorganisms - Melanocytes: produce melanin (a pigment that interferes with UV rays’ ability to reach the nucleus) o Fun fact: people of all skin colors have around the same number of melanocytes; it’s just that more melanin is destroyed, and is also a lighter shade, in paler people - Tactile epithelial cells aka Merkel cells: give us our sense of touch, associated with sensory nerve endings - Dendritic cells aka Langerhans cells: role in immune system (endocytosis, then take it to another part of the immune system for it to be fought) o Star shaped Cells of the epidermis are… - More cuboidal on the deeper layers - More squamous on the superficial layers (since they’re dying and their organelles disappear) Layers of the epidermis:  1. Stratum basale/germinativum: deepest layer a. Attached to underlying dermis b. Cells here are actively dividing (at very rapid rates) c. Contains: keratinocytes, Merkel cells, melanocytes 2. Stratum spinosum a. Spiny appearance, caused by artifacts of histological preparations b. Contains: keratinocytes, dendritic cells 3. Stratum granulosum a. Contains: keratinocytes (last time they’re actually alive) b. Keratohyaline granules: help form keratin c. Lamellated granules: contain a waterproofing glycolipid, which minimizes the constant water loss 4. Stratum lucidum: located only in thick skin a. Composed of a few rows of flat, dead, keratinocytes (squamous) 5. Stratum corneum: most superficial layer a. Thick layer of dead keratinocytes and thickened plasma membranes b. Especially good at protecting skin from abrasions and penetration c. Note: a callous is a thickened area of stratum corneum (additional layers) Notes about the dermis: - Strong, flexible connective tissue - Richly supplied with blood vessels and nerves Layers of the dermis: - Papillary layer: much thinner, superficial o Includes dermal papillae: projections up into the epidermis - Reticular layer: deeper layer o Accounts for 80% of the dermis’ thickness Friction ridges on the fingers (fingerprints): - Arise from the dermis; tall enough that they push up through the epidermis - Use: allows us to grip things without them slipping - Note that another component of your “fingerprint” comes from the sweat you leave behind from the openings of sweat gland ducts Cleavage lines across entire body - Arise from the dermis - Result from the way reticular fibers line up in the dermis - Not visible from surface of the skin - If incision in surgery is parallel to these, it’ll heal better Flexure lines of the hand (creases of palm) - Arise from the dermis - A big reason is that skin around the knuckles is really packed down to the joint - Our hands are also flexed the majority of the time, contributing to these lines Dermal papillae: - Increase surface area between dermis and epidermis  - Helps out with diffusion of substances from the blood supply of the dermis to the alive portions of the epidermis - Help to keep the dermis and epidermis stuck together, in attempts to prevents blisters (when the two get separated) Hypodermis aka superficial fascia - Composed both areolar and adipose connective tissue - Anchors skin to underlying structures - Helps thermally insulate the body o The reason old people are always cold is because the hypodermis thins as we age 3 pigments that contribute to skin color: - Melanin: most important - Carotene: yellowish pigment from carrots and tomatoes o Doesn’t change your skin color a lot, but your diet does have some effect on it - Hemoglobin: RBC protein that, when oxygenated, takes on crimson color o More of a skin color determinant in paler people, because they have such little melanin that you’re essentially seeing through to the blood  Contributes to the pinkish hue of Caucasians