Lab 6_Integument

• Cells change in sturcture and appearance from Stratum Basale to stratum Corneum. This is accomplished by specialized form of Apoptosis (programmed cell death).

• As cells move up through the layers, they become more keratinized, nucleus and organelles break down, and plasma membrane thickens resulting in a tough, protective outer layer that is essential for skin barrier function.

• Cells slough off as dandruff and dander.

• Shed 50,000 cells every minute.

  1. Epidermis. Keratinized stratified squamous epithelium. 5 layers.

• Stratum Corneum. The outermost layer composed of dead keratinized cells that provide a protective barrier against environmental damage, water loss, abrasion, penetration, against biological and chemical assaults.

• Stratum Lucidum. A thin, translucent layer found only in thick skin areas such as the palms and soles, composed of several layers of flattened, dead keratinocytes that contribute to the overall toughness of the epidermis.

• Stratum Granulosum. Cell appearance changes. Keratinization begins. This layer contains keratinocytes that begin to flatten and lose their nuclei, as well as lamellar granules; water resistant glycolipid slows water loss. Cells above this layer die because they are to far from dermal capillaries.

• Stratum Spinosum. Contains web-like system of intermediate prekeratin filaments attached to desmosomes that provide strength and flexibility to the skin. This layer also contains Dendritic (Langerhans) cells, and Macrophages key activator of the immune system.

• Stratum Basale. This is the deepest layer of the epidermis, where cell division occurs. It is primarily composed of a single row of actively mitotic stem cells that produce new keratinocytes(daughters) push upwards to replenish the upper layers of the skin. Melanosomes and Dendritic cells. Melanocytes compose 10 -25% of this layer.

2. Dermis.

Innervated and vascularized.

Contains epidermal hair folicules; Sebaceous glands, and Sudoriferous glands, which play crucial roles in thermoregulation and skin hydration.

• Papillary Layer

• Looser Areolar connective tissue.The uppermost layer of the dermis, characterized by thin collagen fibers and numerous capillaries, providing nutrients to the epidermis and aiding in thermoregulation.

  • Dermal papillae. Small, peg-like projections that interdigitate with the epidermis, increasing the surface area for exchange of gases, nutrients, and waste products.

  • Meissner’s corpuscle ( light touch receptors)

  • Phagocytes, such as macrophages can patrol for microorganisms.

• Reticular Layer.

  • Dense Irregular connective tissue contains elastic fibers that provide strech-recoil properties.

  • Collagen fibers; provide strength and resiliency, allowing the skin to withstand tension and deformation without damage. Binds water

  • Pacinian corpuscle (lamellated) for pressure sentitivity, which are located deeper in the dermis, play a crucial role in detecting deep pressure and vibration, enhancing our tactile perception.

3. Hypodermis (subcutaneous layer)

• Not part of the skin but shares some functions.

• Mostly Adipose tissue that absorbs shock and insulates.

• Anchors skin to underlying structures, mostly muscles.

4. Accessory & Other Structures

• Sebaceous Gland:

  Widely distributed; not in thick skin of palms and soles.

  Most developed from hair follicles and secrete into hair follicles.

  Secrete Sebum; Oily secretion

  Bactericidal

  Softens hair and skin.

• Sudoriferous Gland

  • Eccrine sudoriferous glands: secretory ducts connect to pores that open up at the epidermis. Secretion is sweat; 99% water, electrolytes, antibodies, dermicin (microbe-killing peptide) and metabolic wastes.

  • In all skin surfaces except nipples and parts of external genitalia.

  • Apocrine sudoriferous glands: Secretory ducts empty directly into hair follicles.

  • Hair Shaft

  • Hair Root

  • Hair Papilla

  • Hair Bulb

  • Hair Follicle

  • Arrector Pili Muscle.