A&P Honors: Ch. 5.3 — Papillary Dermis and Reticular Dermis

What is the dermis made up of?

A layer made up of strong, flexible CT.

What are the cells of the dermis?

Fibroblasts, macrophages, and occasional mast cells and white blood cells.

What does the semifluid matrix of the dermis do for the body?

Binds the entire body together like a body stocking. It’s the body’s hide.

How many layers does the dermis have?

Two

What are the two layers of the dermis?

The papillary and the reticular.

What does the papillary dermis consist of?

Areolar CT in which fine interlacing collagen and elastic fibers form a loosely woven mat with many small blood vessels.

What does the looseness of the papillary dermis’ CT allows what?

Phagocytes and other defensive cells to wander freely as they patrol the area for bacteria that have penetrated the skin.

What does dermal papillae do?

Indent the overlying epidermis.

What are house free nerve endings?

Pain receptors.

What are friction ridges?

Skin ridges that consist of epidermal ridges that lie on top of dermal ridges.

What do friction ridges enhance?

Our ability to grip certain kinds of surfaces.

What do friction ridges contribute to? How?

Our sense of touch. By enhancing vibrations detected by the large lamellar corpuscles in the dermis.

How are friction ridges determined?

Genetically.

How much of the thickness of the dermis does the reticular dermis account for?

About 80%

What is the reticular dermis made of?

Coarse, dense irregular CT.

What is the dermal vascular plexus? Where does it lie between?

The network of blood vessels that nourishes this layer. Lies between the reticular dermis and the subcutaneous tissue.

What does the extracellular matrix of the reticular dermis contain?

Thick bundles of interlacing collagen fibers.

What is the reticular dermis named for?

It’s network of collagen fibers.

What are cleavage (tension) lines?

Externally invisible lines that tend to run longitudinally in the skin of the limbs and in circular patterns around the neck and trunk.

Why do surgeons tend to create incisions along cleavage lines?

The skin gapes less and heals more readily.

What do collagen fibers of the dermis give the skin? What does this prevent?

Give skin strength and resiliency that prevent minor jabs and scrapes from penetrating the dermis.

What do elastic fibers provide in the dermis?

The stretch-recoil properties of skin.

What are flexure lines?

Dermal folds that occur at or near joints where the dermis is tight secured to deeper structures.

What can extreme stretching of the skin, such as during pregnancy, do?

Tear the dermis, leaving silvery white scars called stretch marks.

What is another word for stretch marks?

Striae

What can cause a blister?

Short-term but acute trauma from a burn or repeated friction when wielding a hoe.

What is a blister?

A fluid-filled picket that separates the epidermal and dermal layers.