integument

Definition of Membrane: A selective barrier that allows certain substances to pass while not allowing others.
Body Membranes:
- Cover surfaces, cavities, and form protective sheets around organs.
Cyanosis:
- Discoloration of skin (bluish-gray) due to lack of oxygen in the skin; caused by a drop in blood pressure.
- Signals instability in bodily function.

Definition: Covers and lines surfaces; consists of an epithelial sheet combined with an underlying layer of connective tissue (CT).

Cutaneous: Refers to the skin.
- Superficial: Upper or outer side of the body; epithelium composed of keratinizing stratified squamous.
- Two Layers:
1. Epithelial: Stratified squamous epithelium.
2. Connective: Dense irregular fibers of the dermis.

Epidermis Structure:
- Stratum Corneum
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale
Keratinocytes:
- Most numerous cells in epidermis; produce keratin (a protein that contributes to a tough protective layer).
Melanocytes:
- Produce melanin, which helps protect against UV radiation and adds pigmentation to the skin.
- Amount of melanin produced is the same in all individuals, but activity differs, resulting in variation in skin color.
Stratum Basale:
- Deepest cell layer; contains the most nourished keratinocytes that are actively growing and pushing towards the stratum corneum.
Stratum Corneum:
- The most superficial layer; consists of squished dead cell remnants filled with keratin.

Components:
- Hair cells grow in the epidermis, not the dermis.
- Contains vessels and nerve cells.
- The surface between the dermis and epidermis features a papillary wave pattern in the dermis and ridges in the epidermis; this is known as dermal papillae.
- Increases surface area for oxygen and nutrient exchange via diffusion from the interstitial fluid of the dermis.

A. Serous Membranes:
- Composed of a layer of simple squamous epithelium resting on a thin layer of areolar connective tissue (CT).
- Locations in the Body:
- 1. Peritoneum: In the abdominopelvic cavity.
- 2. Pleura: In the thoracic cavity.
- Location of Membrane:
- 1. Parietal: Lines the cavity, pressed against the side (describes the location of the membrane).
- 2. Visceral: Covers structures inside the cavity (describes the location of the membrane).
- 3. Mesentery: Two adjacent sheets of visceral peritoneum in the abdominopelvic cavity.
- 4. Mediastinal Septum: Two adjacent sheets of parietal pleura in the thoracic cavity.
B. Mucous Membranes:
- Composed of various types of epithelium resting on a loose connective tissue membrane; lines all cavities that open to the exterior.

Components of Hair:
1. Hair Follicle: Pit where hair forms, surrounded by dermis.
2. Hair Papillae: Provides blood supply to the hair bulb matrix from the dermis.
3. Hair Bulb: Bottom of the follicle where cells are growing; receives blood/nutrient supply.
4. Root: Part of the follicle that expands into the bulb.
5. Shaft: Portion outside the skin (composed of dead cells).
6. Arrector Pili Muscle: Grows from the epidermis and attaches to the dermis; causes hair to stand up and creates goosebumps.

Sudoriferous (Sweat) Glands:
- Widely distributed throughout the skin; two types:
1. Eccrine Glands: Spread over the body surface; produce thin/watery secretions (sweat) directly onto the body's surface.
2. Apocrine Glands: More restricted distribution; associated with hair follicles in specific regions (pubic, facial, axillary areas); secretions act as airborne pheromones (chemical messengers).
Sebaceous (Oil) Glands:
- Associated with hair follicles; produce oily secretions released into follicles; necessary for keeping hair moist and flexible rather than dry and brittle.
Perspiration: The process of sweating; clear secretion primarily consisting of water, along with salts and uric acids.

Protection:
- Provides mechanical/chemical damage protection (keratin offers a tough barrier), UV radiation protection (melanin), and thermal damage protection (contains receptors for heat, cold, and pain).
Temperature Regulation:
- Heat loss by allowing blood to rush to capillary beds (facilitating sweating); heat retention by constricting blood flow to capillary beds.
Sense Organ Activity:
- Aids in excretion of water/uric acid (perspiration) and in the synthesis of Vitamin D (converted from cholesterol molecules in the skin by sunlight).