The Integumentary, Skeletal, and Muscular Systems
The Integumentary System
- made up of the skin, glands, hair, and nails or claws.
- The integument is composed of all four tissue types and is the largest of
the body’s organ systems.
- skin is an epithelial structure, meaning it covers and protects the
underlying organs from the environment.
- The most fundamental function of skin is to keep the body contents
confined.
- The skin has many functions, such as:
o It protects against excessively humid or dry conditions.
o It protects against environmental chemicals.
o It protects against infectious organisms, such as bacteria,
viruses, fungi, and parasites.
o It helps regulate body temperature.
- If you’re too hot, the blood vessels in your skin dilate (become wider) to
increase blood flow to the skin. Heat radiates out of these blood vessels,
through the skin, and into the environment.
- When you get cold, the skin’s blood vessels constrict (become narrower)
to decrease blood flow to the skin. Less blood flow means less heat
radiates out of the skin, keeping the heat inside the body.
- As the blood vessels dilate, blood pressure drops, and as the blood
vessels constrict, blood pressure increases.
Skin structure
- The skin is comprised of two major layers:
o Epidermis
o Dermis
- Beneath the skin is the hypodermis, or subcutaneous layer, which
supports the epidermis and dermis.
Epidermis
- outermost layer of the skin
- deepest layer of the epidermis is the basal layer, called the stratum
basale
o Three types of cells exist in the stratum basale.
keratinocyte, which produces keratin.
melanocyte, a cell that makes melanin.
, Merkel cell is associated with nerve endings. Merkel cells
with nerve endings make up the Merkel disc. This disc is
what allows for the sensation of touch.
- The next layer is the spiny layer, called the stratum spinosum.
- Above the stratum spinosum is granular layer, called the stratum
granulosum
- The second layer from the surface is the clear layer, called the stratum
lucidum.
- The outermost layer of the epidermis is the horny layer, called
the stratum corneum.
- Cells in the bottom layer are continually dividing. These cells then rise to
the skin’s surface. As the cells move to the surface, they begin dying. By
the time they reach the surface, they’re completely dead
- Keratin is a fibrous protein that provides toughness to the cell and to the
skin.
- fur covering the skin helps to act as a protective barrier so that the skin
itself has only three layers, instead of five.
- These are the three layers of the skin:
o Stratum basale
o Stratum spinosum
o Stratum corneum
dermis
- provides both structural and nutritional support to the epidermis
- only two layers, the thin, superficial papillary layer, and the thick,
deeper reticular layer.
- components consist of fibers, hair follicles, nerve endings, glands,
smooth-muscle blood vessels, lymphatics, fibroblasts, adipocytes, and
macrophages
- fibers found in the dermis consist of collagen, elastin, and reticular fibers.
- Collagen is made of several protein strands braided together
- Reticular fibers are a type of collagen that forms a loose net of thin,
delicate fibers.
- Elastin fibers stretch like rubber bands, giving the skin flexibility.
Hypodermis
- Underneath all the epidermal and dermal structures that make up the skin
is the hypodermis, or subcutaneous layer.
- composed primarily of fat, but also contains blood and lymphatic vessels,
nerves, and connective tissue.
, - stores fat, helps regulate body temperature, and supports the layers
above it—the dermis and epidermis—both structurally and nutritionally.
Pigmentation
- Melanocytes often contain specialized granules that extend from the cell.
These granules contain melanin and are responsible for the variety of skin
colors found in animals.
- Some cells contain many granules and therefore produce dark
pigmentation. Fewer granules result in lighter pigmentation.
Paw pads
- Many animals have footpads composed of thick layers of fat and
connective tissue.
- Some animals can sweat only from their pads and nowhere else.
Planum nasale
- The top of the nose in dogs, cats, sheep, and pigs is referred to as
the planum nasale; in horses and cattle, it’s referred to as the planum
nasolabial.
- made up of only three of the five layers of skin—the stratum basale,
stratum spinosum, and stratum corneum.
Hair
- nonliving structure partially composed of keratin.
- provides warmth; protects the skin from moisture, sunlight, and other
damage; and gives some species distinctive markings for protective or
reproductive purposes.
- Primary hairs, also called coarse or guard hairs, are large, stiff hairs
that provide the rough outer coat of most animals
- Secondary hairs, also called fine hairs, are thinner hairs that make up
the undercoat found on some animals
- tactile—also called sinus—hair, better known as a whisker.
Hair structure
- Hairs are divided into two parts—the shaft and the root.
- The hair shaft is the free portion that rises above the skin surface. It’s
formed from three components layered over one another.
o The cuticle is a single layer of keratinized cells arranged like
shingles on the outside of the shaft.
The Integumentary System
- made up of the skin, glands, hair, and nails or claws.
- The integument is composed of all four tissue types and is the largest of
the body’s organ systems.
- skin is an epithelial structure, meaning it covers and protects the
underlying organs from the environment.
- The most fundamental function of skin is to keep the body contents
confined.
- The skin has many functions, such as:
o It protects against excessively humid or dry conditions.
o It protects against environmental chemicals.
o It protects against infectious organisms, such as bacteria,
viruses, fungi, and parasites.
o It helps regulate body temperature.
- If you’re too hot, the blood vessels in your skin dilate (become wider) to
increase blood flow to the skin. Heat radiates out of these blood vessels,
through the skin, and into the environment.
- When you get cold, the skin’s blood vessels constrict (become narrower)
to decrease blood flow to the skin. Less blood flow means less heat
radiates out of the skin, keeping the heat inside the body.
- As the blood vessels dilate, blood pressure drops, and as the blood
vessels constrict, blood pressure increases.
Skin structure
- The skin is comprised of two major layers:
o Epidermis
o Dermis
- Beneath the skin is the hypodermis, or subcutaneous layer, which
supports the epidermis and dermis.
Epidermis
- outermost layer of the skin
- deepest layer of the epidermis is the basal layer, called the stratum
basale
o Three types of cells exist in the stratum basale.
keratinocyte, which produces keratin.
melanocyte, a cell that makes melanin.
, Merkel cell is associated with nerve endings. Merkel cells
with nerve endings make up the Merkel disc. This disc is
what allows for the sensation of touch.
- The next layer is the spiny layer, called the stratum spinosum.
- Above the stratum spinosum is granular layer, called the stratum
granulosum
- The second layer from the surface is the clear layer, called the stratum
lucidum.
- The outermost layer of the epidermis is the horny layer, called
the stratum corneum.
- Cells in the bottom layer are continually dividing. These cells then rise to
the skin’s surface. As the cells move to the surface, they begin dying. By
the time they reach the surface, they’re completely dead
- Keratin is a fibrous protein that provides toughness to the cell and to the
skin.
- fur covering the skin helps to act as a protective barrier so that the skin
itself has only three layers, instead of five.
- These are the three layers of the skin:
o Stratum basale
o Stratum spinosum
o Stratum corneum
dermis
- provides both structural and nutritional support to the epidermis
- only two layers, the thin, superficial papillary layer, and the thick,
deeper reticular layer.
- components consist of fibers, hair follicles, nerve endings, glands,
smooth-muscle blood vessels, lymphatics, fibroblasts, adipocytes, and
macrophages
- fibers found in the dermis consist of collagen, elastin, and reticular fibers.
- Collagen is made of several protein strands braided together
- Reticular fibers are a type of collagen that forms a loose net of thin,
delicate fibers.
- Elastin fibers stretch like rubber bands, giving the skin flexibility.
Hypodermis
- Underneath all the epidermal and dermal structures that make up the skin
is the hypodermis, or subcutaneous layer.
- composed primarily of fat, but also contains blood and lymphatic vessels,
nerves, and connective tissue.
, - stores fat, helps regulate body temperature, and supports the layers
above it—the dermis and epidermis—both structurally and nutritionally.
Pigmentation
- Melanocytes often contain specialized granules that extend from the cell.
These granules contain melanin and are responsible for the variety of skin
colors found in animals.
- Some cells contain many granules and therefore produce dark
pigmentation. Fewer granules result in lighter pigmentation.
Paw pads
- Many animals have footpads composed of thick layers of fat and
connective tissue.
- Some animals can sweat only from their pads and nowhere else.
Planum nasale
- The top of the nose in dogs, cats, sheep, and pigs is referred to as
the planum nasale; in horses and cattle, it’s referred to as the planum
nasolabial.
- made up of only three of the five layers of skin—the stratum basale,
stratum spinosum, and stratum corneum.
Hair
- nonliving structure partially composed of keratin.
- provides warmth; protects the skin from moisture, sunlight, and other
damage; and gives some species distinctive markings for protective or
reproductive purposes.
- Primary hairs, also called coarse or guard hairs, are large, stiff hairs
that provide the rough outer coat of most animals
- Secondary hairs, also called fine hairs, are thinner hairs that make up
the undercoat found on some animals
- tactile—also called sinus—hair, better known as a whisker.
Hair structure
- Hairs are divided into two parts—the shaft and the root.
- The hair shaft is the free portion that rises above the skin surface. It’s
formed from three components layered over one another.
o The cuticle is a single layer of keratinized cells arranged like
shingles on the outside of the shaft.
