Chapter 3 of 5 - Integumentary System Course
Beneath the epidermis lie two connective tissue layers that provide the skin with its strength, elasticity, blood supply, sensation, and thermal insulation.
The dermis is 15 to 40 times thicker than the epidermis and is composed mainly of connective tissue. It is divided into two regions:
Papillary Dermis (upper)
Reticular Dermis (lower)
Quick Check
Which type of sensory receptor in the dermis detects deep pressure and vibration?
The dermis owes its mechanical properties to two key proteins:
| Protein | Property | Clinical Relevance |
|---|---|---|
| Collagen (type I) | Tensile strength - resists tearing | Decreases with aging (wrinkles); impaired in scurvy (vitamin C deficiency) |
| Elastin | Elastic recoil - stretch and snap back | Degraded by UV exposure (photoaging); reduced in Ehlers-Danlos syndrome |
Langer's lines (cleavage lines) are patterns in the dermis that follow the orientation of collagen bundles. Surgeons cut along these lines to minimize scarring because wounds parallel to collagen fibers heal with less tension.
Fill in the Blank
The protein________provides the dermis with tensile strength and is the most abundant protein in the human body.
| Receptor | Stimulus | Location |
|---|---|---|
| Merkel cells | Sustained light touch | Stratum basale (epidermis) |
| Meissner's corpuscles | Light touch, texture | Papillary dermis |
| Pacinian corpuscles | Deep pressure, vibration | Reticular dermis / hypodermis |
| Ruffini endings | Skin stretch | Reticular dermis |
| Free nerve endings | Pain, temperature | Epidermis and dermis |
Quick Check
What creates the unique fingerprint patterns visible on the skin surface?
The hypodermis lies beneath the dermis. While technically not part of the skin, it is closely associated with the integumentary system and is essential for its function:
The distribution and thickness of the hypodermis varies significantly between body regions, sexes, and individuals. It is thickest on the abdomen and thighs and thinnest on the eyelids and dorsum of the hands.
The skin receives its blood supply through two main vascular plexuses:
Papillary Plexus (superficial)
Capillary loops in dermal papillae - nourish epidermis
Cutaneous Plexus (deep)
At dermis-hypodermis junction - feeds reticular dermis
These plexuses play a critical role in thermoregulation. Arteriovenous anastomoses (AVAs) in the dermis can bypass capillary beds to shunt blood directly from arterioles to venules, rapidly increasing heat loss through the skin surface during vasodilation.
Fill in the Blank
The hypodermis is composed primarily of________tissue, which provides thermal insulation, energy storage, and cushioning for deeper structures.
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