PDBIO 210--Lesson 3 (part 7) --Dermis

What causes wrinkles in the skin?

-- both aging and exposure to UV light cause wrinkles and sagging in the skin --flexibility and thickness of the dermis are affected by UV light and aging (dermis thins and becomes less flexible)

What cells make up the connective tissue of the dermis?

-- cells of connective tissue proper --primarily collagen fibers although does include both elastic and reticular fibers

What is the reticular layer of the dermis? (reticular means network--refers to network of collagen fibers)

-- forms the deep major portion of the dermis -- deep to the papillary layer and superior to the subcutaneous layer (sits in between these 2 layers) --consists of dense irregular CT -- primarily made of collagen fibers **these fibers are interwoven into a large network that surround the structures in the dermis such as hair follicles, sebaceous glands, sweat glands, nerves and blood vessels

What structures are typically found in the reticular layer of the dermis?

-- hair follicles --sebaceous glands --sweat glands --nerves --blood vessels

What are dermal papillae?

-- projections from the dermis that reach towards the epidermis --interlock with epidermal ridges of the epidermis --contains capillaries that supply nutrients to the cells of the epidermis --houses sensory receptors (nerve endings) that continuously monitor touch to the surface of the epidermis

What do blood vessels do?

-- provide nutrients to all living cells epidermis as well as all structures in dermis ** all epithelia including the epidermis are avascular

What are the main functions of the reticular layer of the dermis?

-- provide strength, elasticity and support to the structures of the dermis --provide strength, stretch and elasticity for the skin

What is the papillary layer of the dermis?

-- superficial region of dermis directly adjacent to the epidermis --composed of areola CT --dermal papillae interlock with deep projections of the epidermis called epidermal ridges --contains many nerves (innervation)

How do the dermal papillae and the epidermal ridges work together?

-- together they increase contact between the dermis and epidermis. They connect the two layers together.

What are Stria?

-- when skin is stretched beyond its capability some collagen fibers are torn and result in "stretch marks" -- happens frequently during pregnancy or excessive weight gain

What is the structure of the Dermis

----ranges in thickness from .5 - 3.0 mm --consists of two types of connective tissue (areola and dense irregular) -- 2 major regions: superficial papillary layer and deeper reticular layer

What are the two types of connective tissue of the dermis?

--areolar -- dense irregular

What are the main functions of the dermal papillae?

--bring nutrients to the lower layers of the epidermal cells, they nourish the hair follicles -- help connect the epidermis and the dermis -- houses sensory receptors that monitor touch on the surface of the epidermis --nerves provide innervation

Where are nerve fibers located?

--found throughout the dermis --called innervation --nerve fibers in skin monitor sensory receptors in epidermis and dermis --they control blood flow and gland secretion rates.

What do the nerve fibers in the dermis do?

--help monitor sensory receptors, control blood flow and gland secretion rates

What are lines of cleavage in the dermis?

--identify the predominant orientation of the collagen fiber bundles in the skin --important for surgery, since any cut perpendicular to a line of cleavage results in gaping and scarring (cuts should follow line of cleavage for faster healing)

What is the Dermis?

--lies deep to the epidermis --consists of two type of connective tissue --components include: ** blood vessels ** sweat glands **sebaceous glands **hair follicles **nail roots **sensory nerve endings **smooth muscle tissue --2 major regions of the dermis include: **superficial papillary layer ** deeper reticular layer

How are collagen and elastic fibers organized?

--they are oriented in parallel bundles at specific body locations --alignment of these bundles in the dermis is the result of the direction of applied stress during routine movement --function of these bundles is to resist stress --collagen fibers are tensile strength --elastic fibers provide stretch and recoil during normal movement