Ch 6 Test Yourself Flashcards
Why is skin important? Can you think of six important functions of skin?
- Prevents desiccation and rampant infection
- Covers and protects underlying structures
- Assists in the maintenance of normal body temperature
- Excretes water, salt, and organic wastes
- Serves as a sensory organ, conveying information to the central nervous system
- Engaged in the synthesis of vitamin D and storage of nutrients
Functions are vital for overall health and homeostasis
What is keratinization and why is it an important process?
Keratinization is the process by which keratinocytes undergo changes as they move from the basal layer to the outer layers of the epidermis, filling with keratin and ultimately becoming lifeless sheets. It is important because it provides skin with resiliency and strength through the tough, fibrous, waterproof protein keratin
Millions of dead cells exfoliate daily without harming health
Can you list all five layers of the epidermis?
- Stratum germinativum (basal layer)
- Stratum spinosum (prickle-cell layer)
- Stratum granulosum (granular layer)
- Stratum lucidum (clear layer)
- Stratum corneum
Each layer has distinct characteristics and functions
What happens in the stratum germinativum?
This layer consists of a single row of keratinocytes actively engaged in cell division, replacing exfoliated cells at the skin’s surface
Contains Merkel cells and melanocytes
What is the composition and function of the stratum spinosum?
The stratum spinosum contains several layers of cells held together by desmosomes, providing structural support
Cells in this layer appear spiny when fixed for histologic examination
Describe the stratum granulosum.
It is composed of two to four layers of flattened keratinocytes that begin to degenerate and fill with keratohyalin and lamellated granules, contributing to skin waterproofing
Cells die as they lose vital organelles
How is the skin of hairy animals different from that of humans?
Hairy animals usually have three epidermal layers: stratum basale, stratum spinosum, and stratum corneum. The stratum granulosum and stratum lucidum are generally absent
Five-layered epidermis may occur in thick skin areas
What is the primary difference between the dermis and epidermis?
The dermis is highly fibrous, composed of dense connective tissue, while the epidermis is primarily cellular
The dermis contains hair follicles, nerve endings, glands, and blood vessels
What causes pigmentation of skin?
Pigmentation is caused by the presence or absence of melanin granules in the extensions of melanocytes
Granules concentrated around the nucleus lead to no pigmentation; movement into cellular arms increases pigmentation
How do paw pads differ from other regions of skin?
Paw pads have thick layers of fat and connective tissue, are the toughest skin in the body, and are composed of all five epidermal layers with a thicker stratum corneum
Contains exocrine sweat glands and lamellar corpuscles
What is the structure of the planum nasale in dogs?
The planum nasale has only three epidermal layers, lacks stratum lucidum and stratum granulosum, and has a thinner stratum corneum with deep surface grooves
Contains no glands in the epidermis or dermis
What are the parts of a hair follicle?
- Hair bulb
- Papilla
- Matrix
Each part plays a crucial role in hair development and growth
How does hair form and grow?
Hair grows from the hair follicle, with cells in the hair bulb dividing and keratinizing as they move upward, forming the hair shaft
Hair consists of dead epithelial cells
What are the three cycles of hair growth?
- Anagen (growth phase)
- Telogen (resting phase)
- Catagen (transition phase)
Each phase has distinct characteristics
Why does hair turn gray and then white as animals age?
Decreased melanin production leads to gray hair, and white hair forms when the cortex loses pigment and the medulla fills with air
This change is part of the aging process
What stimulates contraction of the arrector pili muscle?
The sympathetic nervous system stimulates contraction in response to fear or cold
This contraction makes the animal appear larger and traps insulating air
Name two types of sweat glands. How are they different from one another?
- Eccrine sweat glands: simple coiled tube, connected to skin surface
- Apocrine sweat glands: coiled tube, empties into hair follicles
Eccrine glands are found in footpads of dogs
Where are anal sacs found and what is their importance to animals?
Anal sacs are located at the 5 and 7 o’clock positions relative to the anus and act as reservoirs for secretions that mark territory and attract mates
They are expressed during defecation or when frightened
