Understanding Dermal Structures, Thermoregulation, and Skin Cancer
Dermal Accessory Structures
Arrector pili: Makes hair stand up on skin to generate heat when cold.
Hair follicle: Protects the scalp.
Sweat (eccrine) gland: Secretes water to the surface of the skin, causing cooling by evaporation.
Adipose tissue: Stores energy, cushions, and insulates the body.
Sebaceous gland: Secretes sebum to waterproof and lubricate the skin.
Sensory receptors: Respond to stimuli and transmit data.
Dermal papillae: Nourish the epidermal layer.
Blood vessels: Provide nutrients and help regulate body temperature.
Thermoregulation and Epidermal Function
1. Blood clotting (maintaining homeostasis): Achieved by clotting in any damaged regions of the circulatory system.
2. Inflammation: Damaged and dead cells are cleared out, along with bacteria, other pathogens, and debris.
3. Proliferation (growth of new tissue): New tissue and an extracellular matrix to support tissue repair are laid down.
4. Maturation (remodeling): The ability of an organism to keep its body temperature within certain boundaries—even when the surrounding temperature is very different.
Thermoregulation Mechanisms
1. Hot conditions: To prevent the loss of excess heat, such as on a cool day, the body constricts the blood vessels of the skin. This process is known as vasoconstriction.
2. Cold conditions: To cool down, sweat production increases. Drops of sweat form and then evaporate from the skin surface, taking body heat away with them.
Key Skin Components
Melanin: Skin pigmentation formed in melanocytes. Cells are found in the stratum basale and spinosum. Protects the skin and cells of the skin by shielding them from the UV light of the sun.
Keratin: Found in the stratum granulosum, lucidum, and corneum; helps form a protective layer.
Collagen: Found in the dermis; gives the skin its strength and structure and also plays a role in the replacement of dead skin cells.
Carotene: Yellowish pigment found in the corneum and the dermis, more abundant in Caucasians.
Types of Skin Cancer
1. Melanoma: Least common type of skin cancer.
2. Squamous cell carcinoma: Looks like a red, scaly bump and is commonly found on the face.
3. Basal cell carcinoma: Looks like shiny, waxy bumps. Most commonly found in places with high sun exposure.
Membranes and Bone Structures
- Cutaneous: Protective boundary, located on the outside of the body, and is known as the skin.
- Mucous: Lines all body cavities that open to the exterior body surface, aiding in secretion and absorption.
- Serous: Lines open body cavities that are closed to the exterior body surface.
- Synovial: Found in joints, providing cushioning.
Bone Types
Spongy bone: Small needle-like pieces of bone found primarily at the expanded ends of long bones.
Compact Bone: Homogeneous, permeated by an elaborate system of interconnecting vascular canals, the Haversian systems, which contain the blood supply for the osteocytes; the bone is arranged in concentric layers around those canals, forming structural units called osteons.
Skeletal Divisions
Axial: Closer to the median line (vertebrae, head, rib cage, pelvis).
Appendicular: Farther away from the median line (limbs).
Joint Types
Fibrous: Fibrous joints are joined by dense irregular connective tissue that is rich in collagen fibers and do not move.
- Skull bones
Cartilaginous: Joined by cartilage, slightly movable.
- Joints between vertebrae and between the pubic bones
- Epiphyseal plates of growing bones in children
Synovial: Bones are not directly joined. These joints have a synovial cavity and are united by dense irregular connective tissue, making them very movable.
- Knees, elbows, and shoulders, vertebrae