epidemics

Corneal Shedding and Physiological Conditions

  • Cornea and Yellow Pigmentation

    • Mention of "shutting cornea" references possible issues with corneal health.

    • The shedding of the cornea is linked to the perfusion of underlying tissues with blood.

    • Can lead to yellow pigmentation in the skin.

    • Example: Newborn babies often appear yellow within the first 24-72 hours after birth due to normal physiological processes, termed physiologic.

    • The yellow coloration is a result of bilirubin accumulation, which is a component of hemoglobin breakdown.

Autoimmune Attacks and Melanocytes

  • Melanocytes

    • Refers to an autoimmune attack on melanocytes, leading to abnormal patches of depigmentation in the skin, also known as vitiligo.

Structure of Hair

  • Composition of Hair

    • Hair is primarily composed of dead keratinized cells.

    • These cells are filled with keratin and bonded together by intracellular proteins.

  • Visible Parts of Hair

    • Shaft: The portion of hair visible above the skin.

    • Root: The section of the hair below the skin's surface.

    • Follicle: The structure that surrounds the root, anchoring the hair into the skin.

Skin Anatomy

  • Layers of Skin

    • Epidermis: The outermost layer of skin.

    • Dermis: The layer beneath the epidermis that contains various skin structures and facilitates hair growth and sensitivity.

Arrector Pili Muscles

  • Function of Arrector Pili Muscles

    • These muscles are associated with hair follicles and are responsible for causing goosebumps.

    • When contracted, the arrector pili muscles pull the hair upright, making it stand on end.

    • Goosebumps usually occur in response to cold or emotional stimuli as a reflex action.

Types of Muscles

  • Classification

    • The human body contains three types of muscle: smooth, cardiac, and skeletal.

  • Skeletal Muscle

    • Voluntary muscles that are controlled at will (e.g., biceps during arm movement).

  • Smooth Muscle

    • Involuntary muscles found in the digestive system, vasculature, and iris of the eye.

    • Facilitates actions such as peristalsis (movement of food) and vasoconstriction or vasodilation (regulating blood flow).

  • Cardiac Muscle

    • Located in the heart; involuntary muscle that pumps blood throughout the body.

Types of Hair

  • Types of Hair in Newborns

    • Newborns possess a specific soft, fine, downy hair, which is sometimes referred to as lanugo.

    • Lanugo is especially common during fetal development, providing insulation.

    • Other types of hair, although not discussed, can include terminal hair and vellus hair in older children and adults.