Ch 6 Test Yourself Flashcards
Why is skin important? Can you think of six important functions of skin?
Skin’s most important functions include:
* Preventing desiccation and rampant infection
* Covering and protecting underlying structures
* Assisting in the maintenance of normal body temperature
* Excreting water, salt, and organic wastes
* Acting as an important sensory organ
* Engaging in the synthesis of vitamin D and storage of nutrients
Skin serves multiple critical roles in overall health and homeostasis.
What is keratinization and why is it an important process?
Keratinization is the process where keratinocytes move from the basal layer to the outer layers, undergoing changes that lead to the formation of keratin, a tough, fibrous, waterproof protein. This process is important because it enables millions of dead cells to exfoliate daily without harming health.
Keratinization provides skin with resiliency and strength.
Can you list all five layers of the epidermis?
The five layers of the epidermis from innermost to outermost are:
* Stratum germinativum (stratum basale)
* Stratum spinosum
* Stratum granulosum
* Stratum lucidum
* Stratum corneum
Each layer has distinct functions and characteristics.
What happens in the stratum germinativum?
In the stratum germinativum, keratinocytes are actively engaged in cell division and new daughter cells move to more superficial layers as they mature. Merkel cells and melanocytes are also found in this layer.
This layer is crucial for the regeneration of the epidermis.
How does the stratum spinosum get its name?
The stratum spinosum is named for the appearance of cells that contract into speculated masses resembling sea urchins when fixed for histologic examination.
It contains several layers of cells held together by desmosomes.
How does the stratum granulosum contribute to skin function?
The stratum granulosum contributes by containing keratinocytes that fill with keratohyalin and lamellated granules, which leads to cell death and waterproofing of the skin.
This layer plays a vital role in slowing water loss across the epidermis.
How is the stratum lucidum different from other layers?
The stratum lucidum is found only in very thick skin and appears as a translucent layer composed of flattened dead cells.
Most skin lacks this layer, which is crucial for areas requiring extra protection.
How does the skin of hairy animals differ from that of humans?
Skin of hairy animals usually has three epidermal layers: stratum basale, stratum spinosum, and stratum corneum, lacking the stratum granulosum and stratum lucidum.
Some regions may have five-layered epidermis due to slower keratinization.
What are the main differences between the dermis and epidermis?
The dermis is highly fibrous and composed of dense, irregular connective tissue, while the epidermis is primarily cellular. The dermis contains hair follicles, nerve endings, glands, and blood vessels.
The dermis binds the epidermis to underlying tissues and represents the ‘hide’ of the animal.
What causes pigmentation of skin?
Pigmentation is caused by the presence or absence of melanin granules in the armlike extensions of melanocytes. The more granules in the arms and surrounding tissue, the darker the pigmentation.
Granules concentrated around the nucleus do not contribute to visible pigmentation.
How are paw pads different from other regions of skin?
Paw pads are formed by thick layers of fat and connective tissue, are the toughest skin in the body, and consist of all five epidermal layers with a thicker stratum corneum.
They provide protection against abrasion and temperature variances.
What is the structure of the planum nasale?
The planum nasale in dogs has only three epidermal layers, lacking the stratum lucidum and stratum granulosum, and has a thinner stratum corneum composed of 4-8 cell layers.
It features deep grooves and contains no glands in the epidermis or dermis.
What are the main parts of a hair follicle?
The main parts of a hair follicle include:
* Hair bulb
* Papilla
* Matrix
These components are essential for hair growth and development.
How does hair form and grow?
Hair forms from cells in the hair bulb, where the matrix cells divide and push older cells upward, leading to keratinization and the formation of hair.
The hair follicle anchors the hair and is associated with sensory nerve endings.
What are the three cycles of hair growth?
The three cycles of hair growth are:
* Anagen (growth phase)
* Telogen (resting phase)
* Catagen (transition phase)
These cycles regulate the life span of hair.
Why does hair turn gray and then white as animals age?
Hair turns gray due to decreased melanin production and becomes white when the cortex loses pigment and the medulla fills with air.
This change is a natural part of aging.
What stimulates contraction of the arrector pili muscle?
The sympathetic nervous system stimulates arrector pili muscle contraction when an animal is frightened or cold.
This reaction helps animals appear larger and insulates them by trapping air.
What are the two types of sweat glands?
The two types of sweat glands are:
* Eccrine
* Apocrine
Eccrine glands empty onto the skin surface, while apocrine glands empty into hair follicles.
Where are anal sacs found and what is their importance to animals?
Anal sacs are found at the 5 and 7 o’clock positions relative to the anus in cats and dogs, acting as reservoirs for secretions that mark territory when expressed during defecation.
They help transfer the unique smell of the animal to the environment.
