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Hair Glands and Nails

Introduction to Hair Glands and Nails

  • Overview of the video focus on hair glands and nails

  • Importance of understanding hair and associated structures

Hair Structure and Growth

  • Hair has complex accessory structures

  • Average loss of hair: 80 hairs per day

    • Variability based on factors like age, pregnancy, and health

Accessory Structures of Hair

  • Erector Pili

    • Definition: A tiny muscle that contracts to elevate hair strands

    • Function: Causes hair to stand up, creating warmth by trapping air against the skin

    • Phenomenon: Produces goosebumps in response to cold or fear

  • Sebaceous Glands

    • Definition: Glands that produce oil

    • They are not immediately discussed in detail but will be covered later in the lecture

Types of Hair

  • Lanugo

    • Definition: Fine, soft hair covering babies

    • Duration: Typically falls off shortly after birth

  • Vellus Hair

    • Definition: Fine, pale body hair in children and women

  • Terminal Hair

    • Types: Hair on head, pubic hair, eyebrows, and male body hair

    • Development: Influenced by androgens, particularly testosterone

  • Notion: Everyone has some level of testosterone due to adrenal gland activity

Sweat Glands

  • Pseudoriferous Glands (Technical term for sweat glands)

    • Types:

    • Apocrine Sweat Glands

      • Associated with hair follicles

      • Common in armpits and anogenital regions

      • Function: Secrete sweat into hair follicles, tend to produce odor due to bacteria breakdown

    • Eccrine Sweat Glands

      • Not associated with hair follicles

      • Predominantly located in palms of hands and soles of feet

      • Function: Secrete water and electrolytes via exocytosis (a form of marcocrine secretion)

      • Composition: Primarily water with vitamin C, antibodies, and organic waste

Types of Perspiration

  • Insensible Perspiration

    • Definition: Continuous, slow evaporation through the skin

  • Sensible Perspiration

    • Definition: Profuse sweating that can be felt

    • Contexts: Physical exertion, high temperatures (e.g., running in Arizona)

  • Importance of understanding dehydration in burns:

    • Extensive burns compromise the skin’s stratified squamous epithelial layer, increasing risk of dehydration

  • Turgor

    • Definition: A way to assess dehydration by pinching skin and observing how long it takes to return to normal

    • Normal skin should immediately rebound after tenting

Water Gain and Loss through Skin

  • Immersion in hypotonic solutions can result in water absorption through the skin

  • Hypotonic vs. Hypertonic Solutions:

    • Hypotonic: Freshwater, leading to water absorption

    • Hypertonic: Saltwater, leading to dehydration

Triggers for Sweating

  • Heat-induced sweating begins at the forehead; spreads downward

  • Emotionally induced sweating begins at palms, soles, and armpits; spreads eventually

  • Autonomic control: Involuntary response to temperature and emotional states

Sebaceous Glands (Continuation)

  • Characteristics: Holocrine secretion producing an oily substance

  • Activation: Stimulated by hormones, particularly during puberty

  • Locations: Throughout the body, except for palms and soles

  • Acne Formation

    • Blockage of sebaceous glands can lead to Zits

    • Open vs. Closed comedones:

    • Whitehead: Closed comedo

    • Blackhead: Open comedo (oxidized sebum)

Specialized Glands

  • Cereuminous Glands

    • Definition: Earwax-producing glands; a form of apocrine secretion

    • Function: Produces sticky sebum hypothesized to deter insects from entering the ears

  • Mammary Glands

    • Function: Secretes milk; another type of apocrine secretion

    • Development: More prominent in women during pregnancy due to hormonal changes, including:

    • Prolactin

    • Oxytocin

    • Progesterone

    • Estrogen

Nails

  • Definition: Extensions of the epidermis

  • Growth rate: Approximately 1 mm per week

  • Duration for nail growth from cuticle to tip: Approximately six months

  • Note: The instructor has not included questions about nails in exams historically, suggesting lower emphasis in assessments.