The Skin You’re In

Basic Facts Covers the entire body, ~ square meters Covers the entire body, ~ square meters Weighs 4 to 5 kg, around 7% of body weight for an adult. Weighs 4 to 5 kg, around 7% of body weight for an adult. Pliable, yet tough takes a beating everyday! Pliable, yet tough takes a beating everyday!

The Big Layers Epidermis: The keratinized stratified squamous layer consisting of 4-5 distinct layers with 4 distinct cell types Epidermis: The keratinized stratified squamous layer consisting of 4-5 distinct layers with 4 distinct cell types Dermis: The largest layer mainly made of tough fibrous connective tissue. Dermis: The largest layer mainly made of tough fibrous connective tissue. Only dermis has vascular tissue, nutrients reach epidermis by diffusion Only dermis has vascular tissue, nutrients reach epidermis by diffusion Subcutaneous Tissue (aka: hypodermis) Not really a layer of skin but shares some of the skins protective features. Consists mainly of adipose tissue Subcutaneous Tissue (aka: hypodermis) Not really a layer of skin but shares some of the skins protective features. Consists mainly of adipose tissue

Layers of Epidermis 1. Stratum Basale: Deepest epidermal layer, attached to the dermis. A single row of growing, mitotic cells. 1. Stratum Basale: Deepest epidermal layer, attached to the dermis. A single row of growing, mitotic cells. 2. Stratum Spinosum: Several layers thick. Contain thick bundles of pre-keratin 2. Stratum Spinosum: Several layers thick. Contain thick bundles of pre-keratin 3. Stratum Granulosum: Thin (3-5) layers where the keratinocytes change appearance, they start to flatten and cells part break down. Accumulate two types of granules 3. Stratum Granulosum: Thin (3-5) layers where the keratinocytes change appearance, they start to flatten and cells part break down. Accumulate two types of granules A. Keratohyaline: form keratin in upper layers A. Keratohyaline: form keratin in upper layers B. Lamellated: contain a waterproofing glycolipid B. Lamellated: contain a waterproofing glycolipid

4. Stratum Lucidum: Clear layer, a thin band of a few layers of dead keratinocytes, visible only in thick layers 4. Stratum Lucidum: Clear layer, a thin band of a few layers of dead keratinocytes, visible only in thick layers 5. Stratum Corneum: thick layers, where keratin and thick cell membranes protect the skin. Glycolipids help water-proof and keratin toughens 5. Stratum Corneum: thick layers, where keratin and thick cell membranes protect the skin. Glycolipids help water-proof and keratin toughens

Layers vary based on location and thickness. In hands and feet where the epidermis is thick, there is 5 layers. In other areas where it is thinner, the stratum lucidum is missing and the other layers are thinner. Layers vary based on location and thickness. In hands and feet where the epidermis is thick, there is 5 layers. In other areas where it is thinner, the stratum lucidum is missing and the other layers are thinner.

Epidermis Cell Types Cell Types 1. Keratinocytes: Most abundant. Made in the most deep part of the epidermis by cells undergoing continual mitosis. Pushed up by the building of new cells. At the surface they are dead. You lose millions per day and produce a new epidermis every days. In body areas with lots of friction and use epidermis production is faster. 1. Keratinocytes: Most abundant. Made in the most deep part of the epidermis by cells undergoing continual mitosis. Pushed up by the building of new cells. At the surface they are dead. You lose millions per day and produce a new epidermis every days. In body areas with lots of friction and use epidermis production is faster.

2. Melanocytes: Found deep in the epidermis, as melanin is made it accumulates in granules called melanosomes. The melanin granules then accumulate on the “sunny side” of the keratinocytes providing UV protection 2. Melanocytes: Found deep in the epidermis, as melanin is made it accumulates in granules called melanosomes. The melanin granules then accumulate on the “sunny side” of the keratinocytes providing UV protection People all have relatively the same amount of melanocytes, what determines the skin pigmentation is the amount of melanin produced. More melanin, dark skin pigmentation. Exposure to sunlight can also increase the amount of melanin produced. People all have relatively the same amount of melanocytes, what determines the skin pigmentation is the amount of melanin produced. More melanin, dark skin pigmentation. Exposure to sunlight can also increase the amount of melanin produced.

3. Langerhan’s cells: phagocytes which ingest foreign debris in the epidermis. They also help activate the immune system response in the epidermis. 3. Langerhan’s cells: phagocytes which ingest foreign debris in the epidermis. They also help activate the immune system response in the epidermis. 4. Merkel Cells: Present at the dermis- epidermis junction. Associated with sensory nerve endings in the dermis. Function together with these endings to make a touch receptor called Merkel discs. 4. Merkel Cells: Present at the dermis- epidermis junction. Associated with sensory nerve endings in the dermis. Function together with these endings to make a touch receptor called Merkel discs.

Dermis Made of thick connective tissue. (mainly dense irregular) Thus it has the cell types found in connective tissue; macrophages, fibroblasts, some mast cells and WBC’s Made of thick connective tissue. (mainly dense irregular) Thus it has the cell types found in connective tissue; macrophages, fibroblasts, some mast cells and WBC’s Has nerve fibers, lymphatic vessels, and blood vessels, and plenty of them Has nerve fibers, lymphatic vessels, and blood vessels, and plenty of them

Two Layers Papillary Layer: Has areolar connective tissue with many blood vessels. Has projections that extend into the epidermis called dermal papillae. These dermal papillae have: Papillary Layer: Has areolar connective tissue with many blood vessels. Has projections that extend into the epidermis called dermal papillae. These dermal papillae have: Plenty of capillaries to provide blood supply and nerve endings. (Free Nerve Endings and Meissner’s Corpuscles.) Plenty of capillaries to provide blood supply and nerve endings. (Free Nerve Endings and Meissner’s Corpuscles.)

Larger Mounds of these papillae form thick dermal ridges in fingers, palms, and soles of your feet. Fingerprints!! Larger Mounds of these papillae form thick dermal ridges in fingers, palms, and soles of your feet. Fingerprints!!

Reticular Layer ~80% of the dermis ~80% of the dermis Mainly Dense Irregular Connective Tissue Mainly Dense Irregular Connective Tissue Network of blood vessels nourish this layer, found near the subcutaneous layer. Network of blood vessels nourish this layer, found near the subcutaneous layer. The matrix has thick bundles of collagen fibers, in between the thick areas where these bundles are less dense; these areas are called cleavage lines. The matrix has thick bundles of collagen fibers, in between the thick areas where these bundles are less dense; these areas are called cleavage lines.

Sensory Receptors In the Skin Touch (Tactile/Merkel) receptors and Meissner’s Corpsucles. (Similar but separate from Merkel receptors) Both detect light pressure or touch. Touch (Tactile/Merkel) receptors and Meissner’s Corpsucles. (Similar but separate from Merkel receptors) Both detect light pressure or touch. Pacinian Corpuscles: detect deep pressure. But only when first applied, monitors vibrations (dermis – mid/deep) Pacinian Corpuscles: detect deep pressure. But only when first applied, monitors vibrations (dermis – mid/deep) Free Nerve Endings: Respond to pain and temperature mainly. Some are itch and pressure pressure receptors too! In both epidermis and dermis Free Nerve Endings: Respond to pain and temperature mainly. Some are itch and pressure pressure receptors too! In both epidermis and dermis Hair Follicle Receptors: light touch or pressure. Hair Follicle Receptors: light touch or pressure. Ex: insects or a breeze blowing against the skin (dermis/deep)

Glands Sweat (sudoriferous) Glands Sweat (sudoriferous) Glands Eccrine sweat glands: Secretory part lies in a coiled tubule with a duct leading up to the surface. Sweat is released by exocytosis by the glands. Eccrine sweat glands: Secretory part lies in a coiled tubule with a duct leading up to the surface. Sweat is released by exocytosis by the glands. Most numerous of sweat glands, literally you have millions. Main function to control heat/temperature Most numerous of sweat glands, literally you have millions. Main function to control heat/temperature Heat Controls starts at the head and generally moves downward. Stress aka Cold sweat starts at the palms, soles, and armpits, then spreads to other areas Heat Controls starts at the head and generally moves downward. Stress aka Cold sweat starts at the palms, soles, and armpits, then spreads to other areas Minor Excretory Function: Eccrine gland seat is mostly water, some salt, antibodies, metabolic waste, and a protein called dermcidin, which kills microbes. Sweat/Acidic Minor Excretory Function: Eccrine gland seat is mostly water, some salt, antibodies, metabolic waste, and a protein called dermcidin, which kills microbes. Sweat/Acidic

Apocrine Sweat Glands: Their ducts empty into hair follicles. Around 2000, largely around axillary and anogentital areas. Larger than eccrine glands. Contents are same as regular sweat, but also protein and fats. The sweat itself doesn’t smell, but when bacteria on your skin decompose it, then body odor occurs. Apocrine Sweat Glands: Their ducts empty into hair follicles. Around 2000, largely around axillary and anogentital areas. Larger than eccrine glands. Contents are same as regular sweat, but also protein and fats. The sweat itself doesn’t smell, but when bacteria on your skin decompose it, then body odor occurs.

Ceruminous glands= produce wax (ears) Ceruminous glands= produce wax (ears) Mammary glands = milk Mammary glands = milk Both are considered specialized sweat glands Both are considered specialized sweat glands

Sebaceous Glands: Oil glands that secrete sebum. Sebum is usually secreted into a hair follicle, but sometimes on the surface of the skin. Helps lubricate and soften hair and skin. Even provides some bacterial killing action. Sebaceous Glands: Oil glands that secrete sebum. Sebum is usually secreted into a hair follicle, but sometimes on the surface of the skin. Helps lubricate and soften hair and skin. Even provides some bacterial killing action. Blocked sebaceous glands lead to whiteheads and if it dries and oxidizes blackheads. Blocked sebaceous glands lead to whiteheads and if it dries and oxidizes blackheads. Acne is active inflammation of sebaceous glands. Acne is active inflammation of sebaceous glands.

A= Green Eccrine B=Purple Sebaceous C=Teal? Apocrine