Reticular dermis
Reticular dermis · Type I collagen Holds the appendages Scarring layer
The bulk of the dermis: dense irregular connective tissue of thick type I collagen bundles and mature elastic fibres that gives skin its tensile strength and recoil, and the layer in which the appendages, deep vessels and deep mechanoreceptors sit.
Traced from the start
Detail
- Matrix
- Predominantly type I collagen in thick interwoven bundles with elastin, embedded in a ground substance of hyaluronan and proteoglycans
- Cells
- Fibroblasts, mast cells and macrophages; mast cell degranulation here produces the weal and flare of urticaria
- Contents
- Hair follicles, sebaceous and sweat glands, arrector pili, the deep vascular plexus, Pacinian and Ruffini endings
- Langer lines
- Collagen bundles run in preferred directions; incisions placed along them are under least tension and give the finest scar
- Repair
- Injury deeper than the papillary dermis heals by fibrosis rather than regeneration, because dermal collagen is not replaced in its original architecture
When it goes wrong
Wound healing across this layer with excessive collagen deposition
Hypertrophic scar, which stays within the wound margin and may regress, or keloid, which extends beyond it, recurs after excision and is commonest on the sternum, shoulder and earlobe in darker skin
Rupture of dermal collagen under stretch with high glucocorticoid levels (pregnancy, rapid growth, Cushing syndrome, potent topical steroids)
Striae; the purple abdominal striae of Cushing syndrome are wide and atrophic rather than the pale striae of pregnancy
Defective collagen (Ehlers-Danlos syndrome) or excess collagen with vascular obliteration (systemic sclerosis)
Skin hyperextensibility with atrophic scarring and joint hypermobility on one hand; tethered, indurated skin with Raynaud phenomenon and digital ulcers on the other
Practise this structure
16 questions in the bank tagged Skin.
A 45-year-old woman presents with a painful, swollen, red area on her right forearm that developed over the past two days. She reports a minor cut from gardenin…
Mechanisms of disease · common
A 45-year-old woman with diabetes mellitus presents with a painful, rapidly expanding area of redness on her thigh. She has a fever of 39°C (102.2°F) and hypote…
Mechanisms of disease · middle twist
A 65-year-old man presents with purple spots on his forearms and hands that appeared over the past few days. He denies pain, itching, or trauma. His medical his…
Mechanisms of disease · middle twist
A biopsy of the tracheal epithelium shows a single layer of cells with nuclei at different levels, cilia, and mucus-secreting goblet cells. Which of the followi…
Foundations · common
Which of the following is TRUE about stratified columnar epithelium?
Foundations · niche
Which function is performed by stratified cuboidal epithelium?
Foundations · common