Lecture 9 Flashcards
Consists of the skin and its accessory structures including the hair, nails, and glands
Integumentary System
Exterior covering of the body
Skin
Weight of skin
6 pounds in the average adult
Coverage of skin
More than 3000 square inches
Largest organ of the body
Skin
Skin is supplied with
Blood vessels
Nerves
Functions of the skin
Protection Prevents dehydration Regulates body temp Provides sensation Blood reservoir Excretion
Three major regions of the skin
Epidermis
Dermis
Hypodermis
Outermost superficial region
Epidermis
Middle region
Dermis
Superficial fascia
Deepest region
Hypodermis
Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers
Epidermis
Cell types include
Keratinocytes
Melanocytes
Merkel cells
Langerhan’s cells
Function of the epidermis
Protection from external environment
Produce the fibrous protein keratin
Keratinocytes
Produce the brown pigment melanin
Melanocytes
Epidermal macrophages that help activate the immune system
Langerhan’s cells
Function as touch receptors in association with sensory nerve endings
Merkel cells
Layers of the epithelium
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
Outermost layer of keratinized cells
Accounts for three quarters of the epidermal thickness
Stratum Corneum
Another name for stratum corneum
Horny Layer
Functions of the stratum corneum:
Waterproofing Protection Rendering the body insensitive 20-30 cell layers thick 40lbs shed in a lifetime Too far from blood vessels
Between stratum granulosum and corneum
Consists of a few rows of flat, dead keratonicytes or are in the process of dying
Stratum Lucidum
Another name for stratum lucidum
Clear layer
Stratum lucidum is present on in thick skin such as:
Palms of hands
Fingertips
Soles of feet
Thin, 3-5 cell layers in which drastic changes in keratinocyte appearance occurs
Stratum granulosum
Another name for stratum granulosum
Granular layer
Produce keratin and squamous cells flatten as they are pushed upward
Keratinocytes
Accumulate in the cells of the stratum granulosum
Keratohyaline
Lamellated granules
Cells contain weblike system of intermediate filaments attached to desmosomes
Keratinocytes shrink but desmosomes hold in place
Stratum spinosum
Another name for stratum spinosum
Prickly layer
Cells abundant in th stratum spinosum
Melanin granules
Langerhan’s cells
Deepest epidermal layer firmly attached to the dermis
Consists of a single row of the youngest keratinocytes
Stratum Basale
Another name for stratum basale
Basal layer
Alternate name from stratum basale because cells undergo rapid division
Stratum germinativum
Cells found in stratum basale
Melanin
Beneath the epidermis and is composed of connective tissue
Dermis
The dermis contains
Lymphatics Nerves Nerve endings Blood vessels Sebaceous glands Sweat glands Elastic fibers Hair follicles
Cell types of the dermis
Fibroblasts
Macrophages
Mast cells
White blood cells
Role of dermis
Temperature regulation
Two layers of the dermis
Papillary
Reticular
Arranged into microscopic structures that form ridges
These are the finger and footprints
Papillary layer
Beneath the papillary layer
It is a white fibrous tissue that supports the blood vessels
Reticular Layer
Superior surface of the papillary layer that contains peglike projections called
Dermal papillae
Dermal papillae contain
Capillary loops
Meissner’s corpuscles
Free nerve endings
Reticular layer accounts for
80% of the skin thickness
Add strength and resiliency to the skin
Collagen fibers
Provide stretch-recoil properties
Elastin fibers
Composed of adipose and connective tissue
Supports, nourishes, insulates, and cushions the skin
Subcutaneous tissue
or hypodermis
Another name for hypodermis
Superficial fascia
Three pigments that contribute to skin color
Melanin
Carotene
Hemoglobin
Yellow to reddish-brown to black pigment, responsible for dark skin colors
Melanin