The Integumentary system
1. Epidermis
a. Made of epithelial tissue. Top layer of the skin that is simple squamous.
2. Dermis
a. Is vascularized and is made of dense irregular tissue
3. Hypodermis
a. Contains adipose tissue. Absorbs shock and provides insulation.
b. This is what anchors skin to muscles.
Types of Epidermal Cells
1. Keratinocytes
a. These are replaced every 25-40 days
b. Make keratin
c. This is the most abundant cell in the epidermis
d. Tightly compacted cells held together by desmosomes
2. Melanocytes
a. 10-25% of the skin cells.
b. Produce melanin which are packaged in melanosomes and provide us with skin
color.
3. Dendritic
a. Macrophages (Big eater) which are made in bone marrow and migrate to the
epidermis
4. Tactile
a. Sensory touch receptors.
Layers of the Epidermis!
1. Stratum Basale
a. This is the deepest layer. It is attached to the dermis and is a single row of stem
cells.
b. Actively miotic
2. Stratum Spinsosum
a. Several cell layers thick.
b. These cells contain intermediate prekeratin
c. This layer has mostly melanosomes and dendritic cells
d. Called the spikey layer because keratinocytes shrink.
3. Stratum Granulosum
a. 1-5 cell layers thick
b. Cells lose their organelles and their nucleus here and begin to flatten and make
keratin.
c. Cells accumulate lamella granules which help slow down water loss.
4. Stratum Lucidum
1. Epidermis
a. Made of epithelial tissue. Top layer of the skin that is simple squamous.
2. Dermis
a. Is vascularized and is made of dense irregular tissue
3. Hypodermis
a. Contains adipose tissue. Absorbs shock and provides insulation.
b. This is what anchors skin to muscles.
Types of Epidermal Cells
1. Keratinocytes
a. These are replaced every 25-40 days
b. Make keratin
c. This is the most abundant cell in the epidermis
d. Tightly compacted cells held together by desmosomes
2. Melanocytes
a. 10-25% of the skin cells.
b. Produce melanin which are packaged in melanosomes and provide us with skin
color.
3. Dendritic
a. Macrophages (Big eater) which are made in bone marrow and migrate to the
epidermis
4. Tactile
a. Sensory touch receptors.
Layers of the Epidermis!
1. Stratum Basale
a. This is the deepest layer. It is attached to the dermis and is a single row of stem
cells.
b. Actively miotic
2. Stratum Spinsosum
a. Several cell layers thick.
b. These cells contain intermediate prekeratin
c. This layer has mostly melanosomes and dendritic cells
d. Called the spikey layer because keratinocytes shrink.
3. Stratum Granulosum
a. 1-5 cell layers thick
b. Cells lose their organelles and their nucleus here and begin to flatten and make
keratin.
c. Cells accumulate lamella granules which help slow down water loss.
4. Stratum Lucidum
