Human Anatomy
General Features of Skin and Fascia
Skin and fascia anatomy for MBBS: epidermis, dermis, appendages, superficial and deep fascia and dermatomes, mapped to NMC codes AN4.1 to AN4.5.
MedNext Academy | 3 min read
General Features of Skin and Fascia
Skin and fascia anatomy for MBBS: epidermis, dermis, appendages, superficial and deep fascia and dermatomes, mapped to NMC codes AN4.1 to AN4.5.
This chapter describes the skin as the largest organ and the layers of fascia that lie beneath it. It covers the structure of thick and thin skin, its appendages, the arrangement of superficial and deep fascia, and clinically useful ideas such as cleavage lines and dermatomes.
High-yield: General Features of Skin and Fascia
- Skin has two layers: the outer epidermis, which is avascular epithelium, and the deeper dermis, which is connective tissue.
- Thick skin, as on the palm and sole, is hairless and has a thick keratin layer, while thin skin covers the rest of the body.
- Skin appendages include hair follicles, sebaceous glands, sweat glands and nails.
- The superficial fascia is a layer of loose connective tissue and fat lying deep to the skin.
- The deep fascia is a dense fibrous sheet that invests muscles and forms intermuscular septa.
- Deep fascia is absent over the face, where the superficial fascia contains the muscles of expression.
- Skin creases and cleavage lines run parallel to the collagen bundles of the dermis.
- A surgical incision along a cleavage line heals with a finer scar than one across it.
- Dermatomes are strips of skin supplied by a single spinal nerve and are used to map sensory loss.
- Cutaneous nerves reach the skin by piercing the deep fascia along fairly constant lines.
- The colour of skin depends mainly on melanin produced by melanocytes in the epidermis.
- The superficial fascia of the anterior abdominal wall below the umbilicus has a fatty layer and a membranous layer.
- The membranous layer of superficial fascia continues into the perineum and helps direct extravasated urine.
- Modified sweat glands include the ceruminous glands of the ear and the mammary glands.
Layers deep to the surface
- **Epidermis:** Avascular keratinised stratified squamous epithelium; thickest on palms and soles.
- **Dermis:** Vascular connective tissue carrying nerves, vessels and appendages; gives skin its strength.
- **Superficial fascia:** Loose connective tissue and fat; may hold platysma and other muscles in the neck and face.
- **Deep fascia:** Dense fibrous sheet investing muscles; forms septa, retinacula and intermuscular partitions.
NMC competencies in this chapter
- **AN4.1:** Structure and appendages of skin
- **AN4.2:** Types of skin and skin creases
- **AN4.3:** Superficial fascia and its modifications
- **AN4.4:** Deep fascia and its modifications
- **AN4.5:** Dermatomes and their clinical relevance
Frequently Asked Questions
What is the difference between thick and thin skin?
Thick skin, found on the palms and soles, is hairless and has a very thick keratin layer for protection. Thin skin covers the rest of the body and carries hair follicles and associated glands.
Why do cleavage lines matter to surgeons?
Cleavage lines follow the collagen bundles in the dermis. An incision made along them gapes less and heals with a finer scar, so surgeons plan incisions parallel to these lines when possible.
What is a dermatome?
A dermatome is the strip of skin supplied by a single spinal nerve. Mapping dermatomes lets a clinician localise the level of a nerve or spinal cord lesion from the pattern of sensory loss.
How is superficial fascia different from deep fascia?
Superficial fascia is loose fatty connective tissue just beneath the skin, whereas deep fascia is a tough fibrous sheet that wraps muscles and forms septa and retinacula.
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