Dermis and Its Functions

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Questions and Answers

What is a characteristic feature of fibroblast-related acanthosis nigricans?

Causes increased growth factor receptor signaling. (correct)

Occurs primarily in the scalp.

Is common in elderly males.

Leads to significant hair loss.

Which of the following best describes mastocytosis?

Only affects adults over the age of 50.

An increase in melanocytes in the skin.

A condition characterized by a reduction in mast cells.

A spectrum of diseases involving increased mast cells. (correct)

What primary component mainly constitutes the dermis?

Collagen (correct)

Hyaluronic acid

Adipose tissue

Elastic tissue

Which structure provides a prominent boundary between the dermis and the epidermis?

Dermal papillae Signup and view all the answers

What is the primary function of the hypodermis?

Stores fat and provides insulation. Signup and view all the answers

Which layer is located directly below the dermis?

Hypodermis. Signup and view all the answers

What is one of the functions of the dermis related to temperature control?

Vasoactive regulation Signup and view all the answers

Which cell type in the dermis is involved in the inflammatory response?

Neutrophils Signup and view all the answers

How does the hypodermis contribute to hormonal functions?

It converts androstenedione to estrone. Signup and view all the answers

What term is used to refer to the dermis?

Corium Signup and view all the answers

What developmental origin do the constituents of the dermis have?

Mesodermal Signup and view all the answers

Which of the following is NOT a function of the dermis?

Digestion Signup and view all the answers

What structures do nerve endings in the dermis primarily surround?

Hair follicles Signup and view all the answers

What type of connective tissue primarily composes the reticular layer of the dermis?

Dense, irregular connective tissue Signup and view all the answers

Which mechanoreceptor is specifically involved in sensing deep pressure and vibratory sensation?

Pacinian corpuscles Signup and view all the answers

Which collagen types are primarily found in the dermis?

Type I and Type III collagen Signup and view all the answers

What is the primary function of elastic fibers in the dermis?

Allow for gliding, stretching, and recoiling Signup and view all the answers

What role do the capillaries in the papillary layer of the dermis serve?

Nutrient supply and waste removal Signup and view all the answers

What is the main characteristic of the papillary layer of the dermis?

Richly supplied with blood vessels and sensory nerve endings Signup and view all the answers

Which cells are responsible for providing sensitivity to light touch in the skin?

Meissner's corpuscles Signup and view all the answers

How is collagen primarily produced in the dermis?

By fibroblasts in the rough endoplasmic reticulum Signup and view all the answers

What is the primary function of fibroblasts in the dermis?

Production and secretion of collagen and elastic fibers Signup and view all the answers

Which type of elastic fibers is found near the junction of the papillary and reticular dermis?

Elaunin fibers Signup and view all the answers

What is the role of mast cells in the dermis?

Secrete vasoactive and proinflammatory mediators Signup and view all the answers

What are reticular fibers primarily composed of?

Type III collagen Signup and view all the answers

Where in the dermis are oxytalan fibers predominantly found?

In the papillary dermis Signup and view all the answers

Which type of cells assists the immune response in the connective tissue?

Histiocytes Signup and view all the answers

What is the function of dermal adipocytes?

Insulation and energy storage Signup and view all the answers

What triggers thermoreceptors sensitive to cold?

Temperatures below 20 degrees Celsius Signup and view all the answers

Which statement about the vasculature of the dermis is true?

It is composed of arteries and veins that form a cutaneous plexus. Signup and view all the answers

What are Ruffini's corpuscles primarily sensitive to?

Pressure, stretching, and distortion of the skin Signup and view all the answers

Ehlers-Danlos syndrome is primarily caused by defects in which of the following?

Collagen synthesis Signup and view all the answers

What condition is characterized by brittle bones that fracture easily?

Osteogenesis imperfecta Signup and view all the answers

Striae distensae commonly develop due to what?

Rapid skin stretching or shrinking Signup and view all the answers

What are keloids characterized by?

They grow beyond the boundaries of the original wound Signup and view all the answers

Which condition is associated with abnormal fibroblast function, resulting in itchy and painful skin patches?

Lichen sclerosus Signup and view all the answers

Which of the following is NOT a characteristic of hypertrophic scars?

They extend beyond the original wound boundaries Signup and view all the answers

Study Notes

Dermis

The dermis is a connective tissue layer that resides beneath the epidermis, making up the majority of the skin.
Its thickness ranges from 0.2 mm (eyelids) to 4 mm (palms, soles).
Contains blood vessels, sweat glands, sebaceous glands, nerve endings, hair follicles, and nail roots.
It's also known as corium.
The dermis has a wavy boundary with the epidermis.
- Dermal papillae are finger-like extensions of the dermis that project upward into the epidermis.
- Epidermal ridges are downward waves of the epidermis.
- Friction ridges are prominent waves found on fingers, creating fingerprints.
The cells of the dermis are mesodermal in origin, except for nerves and melanocytes, which derive from the neural crest.

Functions of the Dermis

Skin support: Provides pliability, elasticity, and tensile strength through collagen, hyaluronic acid, oxytalan fibers, and elastic tissue.
Protection: Protects the body from mechanical injury.
Thermoregulation: Vasoactive dermal vessels regulate body temperature, and glomus bodies contribute through AV shunt formation.
- Glomus bodies are found in digits, palms, and soles, consisting of glomus cells, vessels, and smooth muscle.
Sensation: Nerve endings in the dermis surround hair follicles, acting as mechanoreceptors for hair movement. Deep pressure receptors are also present.
- Pacinian corpuscles: Deep pressure and vibration sensation.
- Meissner's corpuscles: Low-frequency stimuli.

Layers of the Dermis

Papillary Layer: Superficial zone that projects into the epidermal ridges.
- Composed of loose connective tissue.
- Thin zone of areolar tissue with capillaries, sensory nerve endings, and cytoplasm.
- Allows for mobility of leukocytes and defense cells.
Reticular Layer: Deeper and thicker layer, made of dense, irregular connective tissue.
- Connects with the subcutaneous fatty tissue.
- Contains blood vessels and nerves.

Interstitial Components

Collagen:
- Primary component of the dermis, making up 70% of its weight.
- Predominantly Type I collagen with some Type III.
- Found in tendons, ligaments, bone lining, and the dermis.
- Provides stress resistance.
- Degraded by collagenases and replaced by new fibers.
- Collagen fibers are aggregations of fibrils.
  - Thin fibers in the papillary layer.
  - Thick fibers in the reticular layer.
Elastic Fibers:
- Composed of elastin and fibrillin microfibrils.
  - Elastin allows for gliding, stretching, and recoiling.
- Thinner, less tough than collagen fibers.
- Abundant in the dermis of the scalp, face, and extensible organs.
- Deeper fibers are thicker.
- In the reticular layer, they run parallel to the skin surface.
- Connected to the lamina densa of glands, sweat ducts, smooth muscle, nerves, and blood vessels.
- Subtypes:
  - Elaunin Fibers: Found near the papillary-reticular junction.
  - Oxytalan Fibers: Found in the papillary dermis, perpendicularly arranged.
Reticular Fibers:
- Composed of Type III collagen.
- Thin reticular network compared to collagenous fibers.
- Found in various tissues, forming supporting frameworks.

Cells of the Dermis

Fibroblasts:
- Primary cell type in the dermis.
- Produce and secrete procollagen and elastic fibers.
- Procollagen is catalyzed to form collagen, which is then cross-linked into strong layers.
Macrophages (Histiocytes):
- Tissue macrophages that intermingle with fibroblasts and help the immune system.
- Assist in organ repair.
Mast Cells:
- Found in the perivascular areas.
- Secrete vasoactive and proinflammatory mediators.
- Contain granules with histamine and other chemicals.
Schwann Cells: Specialized cutaneous Schwann cells initiate pain sensation.
Dermal Adipocytes:
- Distinct from subcutaneous adipocytes.
- Involved in insulation, energy storage, hair follicle regeneration, and wound healing.

Vasculature

Subcutaneous/Deep Dermal:
- Arteries and veins branch superficially into the middermis, forming the cutaneous plexus.

### Nerve Endings

Free-Nerve Endings: Sensitive to cold, found throughout the body, lips, tongue, and conjunctiva.
Brushes of Ruffini: Detect tension deep in the skin, sensitive to pressure, stretching, and distortion.

Diseases

Collagen-Related:
- Ehlers-Danlos Syndrome: Genetic connective tissue disorders.
  - Defective collagen synthesis.
  - Symptoms: skin hyperextensibility, joint mobility, tissue fragility.
- Osteogenesis Imperfecta: Genetic disorder of type I collagen.
  - Decreased dermal collagen, impaired skin elasticity, brittle bones.
- Striae Distensae: Stretch marks caused by rapid stretching or shrinkage of the skin.
  - Rupture of collagen and elastin.
Fibroblast-Related:
- Hypertrophic Scars: Raised, erythematous, pruritic lesions confined to the wound boundaries, caused by myofibroblasts.
- Keloids: Benign growths of fibrous tissue extending beyond the wound boundaries, also related to myofibroblasts.
- Lichen Sclerosus: Inflammatory disorder with abnormal fibroblast function, causing dermal fibrosis and epidermal changes.
- Acanthosis Nigricans: Increased growth factor receptor signaling, leading to epidermal and dermal proliferation.
Mast Cell-Related:
- Mastocytosis: Increase in mast cells in the skin and other organs.
  - Urticaria Pigmentosa: Reddish-brown lesions that form hives or blisters when stroked.

Hypodermis

Also called the subcutaneous layer or superficial fascia.
Connects the skin to underlying fascia of bones and muscles.
Composed of well-vascularized loose areolar connective tissue and adipose tissue.
Functions: fat storage, insulation, and integument cushioning.
The panniculus (subcutaneous layer) varies in thickness based on the skin site.
Considered an endocrine organ due to hormone conversions:
- Androstenedione to estrone by aromatase.
- Lipocytes produce leptin, which regulates body weight.

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Description

Explore the structure and functions of the dermis, the connective tissue layer beneath the epidermis. This quiz covers its components, such as blood vessels and glands, as well as its role in skin support and protection. Discover the unique features that contribute to the dermis' essential functions.