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    Related Topics

    From Integumentary System

    Nail Plate
    Hard, visible part of the nail.
    Hair
    Strands of keratinized cells that grow from follicles beneath the skin.
    Reticular Layer
    Deeper dermal layer, housing collagen and elastin fibers.
    Hemoglobin
    Oxygen-carrying protein in blood responsible for the red coloration of skin.
    Hair Papilla
    Cluster of cells at the base of the hair follicle containing capillaries.
    Merkel Discs
    Receptors that detect light touch and pressure.
    Lamellated (Pacinian) Corpuscles
    Receptors that detect deep pressure and vibration.
    Nail Bed
    Skin under the nail plate, supplying nutrients.
    Dermal Papillae
    Extensions of the dermis into the epidermis that provide nutrients and sensory functions.
    Adipose Tissue
    Fat tissue in the hypodermis that insulates and stores energy.
    Mammary Glands
    Glands in females that produce milk during lactation.
    Carotene
    Pigment contributing to the yellow-orange coloration of the skin.
    Melanin
    Pigment responsible for skin color.
    Stratum Granulosum
    Layer of epidermis where keratinization begins.
    Hair Root
    Part of hair within the follicle, undergoing growth.
    Eccrine Sweat Glands
    Most common sweat glands, found all over the body.
    Sweat Glands
    Glands that produce sweat to regulate body temperature.
    Stratum Lucidum
    Layer found only in thick skin, providing extra protection.
    Hair Follicle
    Root of the hair embedded in the skin.
    Sensory Nerve Endings
    Nerve endings in the skin that detect sensory information.
    Pheomelanin
    Type of melanin that produces yellow and red pigmentation.
    Cuticle
    Eponychium; tissue at the base of the nail that protects the matrix.
    Hair Bulb
    Base of the hair follicle where cells divide and produce the hair shaft.
    Nails
    Hard, keratinized extensions at the tips of fingers and toes.
    Stratum Basale
    Deepest layer of epidermis responsible for cellular regeneration.

    Sebaceous Glands

    Reviewed by our medical team

    Glands that produce sebum (oil) to lubricate skin and hair.

    1. Overview

    Sebaceous glands are holocrine exocrine glands associated with the skin that secrete an oily substance known as sebum. These glands are a key component of the integumentary system and are involved in lubricating and waterproofing the skin and hair. Sebaceous glands play essential roles in maintaining skin barrier integrity, antimicrobial defense, and thermoregulation. Their activity is hormonally regulated and closely linked to conditions such as acne and seborrheic dermatitis.

    2. Location

    Sebaceous glands are distributed throughout most of the body’s skin, with varying densities depending on the region:

    • High density: Face, scalp, chest, and upper back—areas prone to oiliness and acne.

    • Moderate density: Trunk and limbs.

    • Absent: Palms of the hands and soles of the feet.

    • Association with hair follicles: Most sebaceous glands open into hair follicles and are considered part of the pilosebaceous unit.

    • Free sebaceous glands: Found in hairless regions such as the eyelids (Meibomian glands), lips (Fordyce spots), and genital mucosa.

    3. Structure

    Sebaceous glands are composed of lobular clusters of specialized epithelial cells:

    • Acini (lobules):

      • Grape-like clusters of sebocytes that synthesize and store sebum in cytoplasmic lipid droplets.

      • Located in the dermis, near the upper portion of hair follicles.

    • Duct system:

      • Short duct connects the acini to the hair follicle or directly to the skin surface in hairless regions.

    • Holocrine secretion:

      • Mature sebocytes rupture, releasing their entire contents (sebum) into the duct.

    Sebaceous glands are surrounded by a basal layer of progenitor cells that continually replenish the sebocytes.

    4. Function

    Sebaceous glands perform several critical functions essential to skin health:

    • Sebum secretion: Oily, lipid-rich secretion that coats the skin and hair shaft.

    • Lubrication: Prevents drying and cracking of the epidermis and hair.

    • Waterproofing: Helps reduce transepidermal water loss by forming a hydrophobic barrier.

    • Antimicrobial action: Sebum contains free fatty acids and lipids with antibacterial and antifungal properties.

    5. Physiological role(s)

    Sebaceous glands contribute to several broader physiological processes:

    • Skin barrier maintenance: Supports stratum corneum integrity and normal desquamation (shedding).

    • Hormonal response: Androgens (e.g., testosterone) stimulate sebaceous gland growth and sebum production, especially during puberty.

    • Innate immunity: Sebum forms part of the skin’s first-line defense against pathogens.

    • Thermoregulation support: Although not directly involved in sweating, sebum influences surface heat and moisture retention.

    6. Clinical Significance

    Sebaceous glands are involved in a range of dermatological and systemic conditions:

    • Acne vulgaris:

      • Caused by excess sebum, follicular hyperkeratinization, bacterial overgrowth (Cutibacterium acnes), and inflammation.

      • Most common during adolescence due to androgenic stimulation.

    • Seborrheic dermatitis:

      • Inflammatory condition associated with overactive sebaceous glands and yeast colonization (Malassezia).

    • Sebaceous cysts (epidermoid cysts):

      • Blocked sebaceous ducts may form fluid-filled sacs that can become infected or inflamed.

    • Sebaceous hyperplasia:

      • Benign enlargement of sebaceous glands, typically seen as yellowish papules on the face in older adults.

    • Sebaceous gland carcinoma:

      • Rare but aggressive malignant tumor, often arising in Meibomian glands of the eyelid; requires early diagnosis and treatment.

    • Hormonal disorders:

      • Conditions such as polycystic ovary syndrome (PCOS) and androgen-secreting tumors can cause sebaceous overactivity and oily skin.

    Did you know? The skin has a natural protective barrier called the acid mantle, which helps keep bacteria and other microorganisms from entering the body.