Pt 2.1
Telogen effluvium
"Blowing the coat"; the overall hair loss that occurs from the hair follicles being in a synchronized telogenic phase. It may be brought on by many factors, such as stress, medication, malnutrition, and postpartum hormonal changes in dogs.
sweat glands
"sudoriferous glands" 2 types: eccrine and apocrine
list three major functions of feathers (test yourself 21-2)
(1) flight (2) protection of the thin skin from trauma, rain, and excessive radiation from sunlight (3) thermoregulation, camouflage, and communication behaviors, such as courtship, defense, and recognition
functions of feathers
- flight - protect skin from trauma, rain, excessive radiation from sunlight - thermoregulation - camouflage - communication behaviors (courtship, defense, recognition)
integument
- protects and covers underlying structures and forms a critical barrier b/w inner body and environment - synthesis of vitamin D and storage of nutrients - takes in information via pressure and touch skin, horns, hooves, claws, glands, hair
modifications in bird skeleton for flight
- reduction in # of bones - fusion of bones to form plates that provide strength and simplify movements - reduction in density of bones - loss of internal bone matrix (bones generally hollow and filled with air spaces
what are the three cycles of hair growth? (test yourself 6-3)
1. Anagen is the time of hair growth. 2. Telogen occurs when the maximum length of hair is achieved, the hair stops growing, the hair follicle shortens, and the hair is held in a resting phase. 3. Catagen is the period of transition between the anagen and telogen phases.
Why is skin important? Can you think of six important functions of skin? (Test yourself 6-1)
1. covers and protects underlying structures. 2. prevents desiccation and reduces the threat of injury. 3. assists in the maintenance of normal body temperature via sweating and shivering and the presence of features such as hair and sebaceous glands. 4. excretes water, salt, and organic wastes.
skin of birds
2 layers: dermis and epidermis
epidermal layers in hairy animals
3 layers stratum basal, spinosum, and corneum
Hypodermis (subcutaneous layer)
3rd layer of the skin; Consists of connective tissue which binds the skin to the underlying muscle. composed primarily of adipose tissue (insulation and shock-absorbing)
what is a blood feather? (test yourself 21-2)
A blood feather is a growing feather. Blood can be seen in the proximal part of the feather shaft during the entire growth phase. Injury to a blood feather not only results in bleeding but can prevent a feather from developing normally until molted again.
Define a fault bar. What causes it? (test yourself 21-2)
A fault bar (stress bar) is a weakened area on the feather vane where the barbs lack barbules. If a feather is stressed during its growth, even for a few hours, there is an interruption in its blood flow and a fault bar develops. When the stressor is removed, the blood supply is returned and normal development continues. The most common stressor is a poor diet.
behavioral thermoregulation
Actions or reactions of an organism to the environment (ex. hibernation) to regulate body temp
define ectothermic (test yourself 22-1)
Amphibians and reptiles are commonly referred to as ectothermic or cold blooded. Ectothermic animals are unable to generate body heat internally; therefore, their body temperatures are dependent on environmental temperatures
what is a drink patch? (test yourself 22-2)
An area of the skin with increased permeability, usually on the animal's ventral surfaces. This is especially evident in amphibians, so they do not need to drink water.
what is preferred optimal temperature zone (POTZ)? (test yourself 22-1)
An ectotherm's ability to effectively thermoregulate is entirely dependent on access to temperatures within the animal's preferred optimal temperature zone (POTZ), which is a range of temperatures in which the animal can perform all necessary metabolic functions. This principle becomes very important when maintaining herptiles in captivity. If not provided with an appropriate thermal gradient, a herptile will not be able to thermoregulate efficiently. When provided with inappropriately low temperatures, ectothermic animals can suffer from digestive problems, immunosuppression, and other disorders. If kept at temperatures that are too high, the animals are forced to maintain a high metabolic rate and may suffer from energy deficits
Why does hair turn gray and then white as animals age? (test yourself 6-3)
As animals age, melanin production decreases, and the hair begins to turn gray. White hair is formed when the cortex loses its pigment entirely and the medulla becomes completely filled with air.
arrector pili muscle
Causes hair to stand on end and goose bumps to appear why hair may stand up on frightened cat's back
the nasolacrimal duct system is absent in what order of reptiles? (test yourself 22-3)
Chelonians do not possess nasolacrimal ducts. The tears spill over the lid margin, so some degree of epiphora is normal in healthy animals.
How are paw pads and the planum nasale different from other regions of skin? (test yourself 6-2)
Digital pads are formed by thick layers of fat and connective tissue that bear the weight of the animal. The pad's outer surface is the toughest and thickest skin in the body. - often pigmented and composed of all five epidermal layers. stratum corneum is thicker than all the others combined. This tough outer skin together with insulating fat forms a protective barrier against abrasion and thermal variances, enabling the animal to walk on rough surfaces, hot roads, and cold snow. The surface of the pad feels rough, and an uneven surface is visible to the naked eye. The pad is composed of exocrine sweat glands and lamellar corpuscles. Histologically, the ducts from these sweat glands can be seen passing through the dermis to the stratum basale of the epidermis. Their glandular excretion is then excreted onto the surface of the pad. The planum nasale is usually pigmented and appears to be a tough, thick region of integument histologically; however, the planum nasale in the dog is composed of only three epidermal layers, with the stratum lucidum and stratum granulosum absent. The outermost layer, the stratum corneum, is composed of only four to eight cell layers, surprisingly thin considering the exposed location of the nose and its heavy use, particularly in the dog. The epidermal surface of the planum nasale is divided by deep surface grooves, giving it the appearance of being composed of multiple plaques. As with other regions of the skin, the dermis and epidermis interdigitate to form an irregular line of attachment that includes dermal papillae. Although often moist from nasal secretions and licking, the planum nasale in the dog contains no glands in the epidermis or dermis. However, in the sheep, pig, and cow, tubular glands are found.
Can you list all five layers of the epidermis? What is happening in each layer? (Test yourself 6-1)
From the innermost layer outward: 1. stratum basale (basal layer). consists of a single row of keratinocytes, which are firmly attached to the epithelial basement membrane and actively engaged in cell division. New daughter cells move from the stratum basale to sequentially more superficial layers as they mature. In this way, they replace epithelial cells that have exfoliated at the skin's surface. Merkel cells and melanocytes are found in this layer. 2.stratum spinosum (the prickle-cell layer). when the cells of this epidermal layer are fixed for histologic exam, they contract into speculated masses that resemble sea urchins. It contains several layers of cells that are held together by desmosomes. 3. The stratum granulosum (granular layer): middle layer of skin. Composed of two to four layers of flattened, diamond-shaped keratinocytes, is the highest level of the epidermis where living cells can be found. The cytoplasm of these cells begins to fill with keratohyalin and lamellated granules, which in turn leads to the dramatic degeneration of the nucleus and other organelles. Without these vital parts, the cell quickly dies. The lamellar granules contain waterproofing glycolipids and are transported to the periphery of the cell, where their contents are discharged into the extracellular space. These glycolipids play an important role in waterproofing the skin and slowing water loss across the epidermis. 4. The stratum lucidum (clear layer): found only in very thick skin. Most skin, therefore, lacks this layer. Microscopically, appears as a translucent layer composed of a few rows of flattened dead cells. In this and the outermost epidermal layer, the sticky contents of the keratogranules combine with intracellular tonofilaments to form keratin fibrils. 5. The stratum corneum (horny layer): outermost layer and dominates the epidermis. It constitutes up to three quarters of the total epidermal thickness and is composed of 20 to 30 rows of keratinocytes. On sagittal section, the cells are paper thin and almost two dimensional, yet when viewed from above, they appear hexagonal. These are really only the remnants of keratinocytes, because the actual cells died in the stratum granulosum. They are sometimes called horny or cornified cells, but we commonly call them dandruff and recognize them as the flakes that occasionally drop on our shoulders.
claws
Hard, often pigmented outer coverings of the distal digits. important for traction while running, walking, climbing, and for protection or catching prey
Describe the parts of the hair follicle and explain how hair grows
Parts of hair follicle: - hair bulb: deepest - papilla: dermal cells at base of hair bulb - matrix: composed of rapidly dividing epidermal cells that are supplied with important nutrients from the blood vessels how hair grows: - Nourishment of the epithelial cells stimulates much cell division and growth. As the cells divide, older cells are pushed upward into the tunnel away from the papilla. These cells become keratinized, and as they lose contact with the nutrition provided by the papilla, they die and become part of the developing hair. In this way hair is constructed from dead epithelial cells.
List and describe the three types of hair.
Primary (guard) hairs: straight or arched; thicker and longer than secondary hairs. They are the dominant hairs in a complex hair follicle. Secondary (satellite/wool-type) hair: softer and shorter than primary hairs. wavy or bristled in dogs and are the predominant hair type in species with wool-type coats. Tactile hairs: used as probes and feelers. well supplied with sensory endings that make them particularly sensitive to the slightest bending or touch. These hairs are commonly known as whiskers and can be found around the mouth and on the muzzle of many species, as well as mixed intermittently throughout the hair coat. The tactile hair is also called the sinus hair because of the presence of a large blood sinus, which is located in the connective tissue portion of the follicle.
Preferred Optimal Temperature Zone (POTZ)
Range of temps that all metabolic functions can be met/performed at Keep animals in that range when administering medications/drugs
How does the reptile iris differ from that of mammals? Why is this clinically important? (test yourself 22-3)
Reptiles are similar to birds in that the iris is made up of skeletal muscle and is under voluntary control. In mammals, the iris is under involuntary control. Therefore, mydriatic agents used to dilate the pupil for ophthalmic examinations in mammals are not effective in reptiles. A direct pupillary light response is usually noted, but consensual reflexes are often not seen.
what structures are derivatives of a bird's skin and what are they made of? (test yourself 21-1)
Scales, feathers, and the outer sheath of beaks and claws are made of keratin, which is produced by epithelial cells.
How is the skin of hairy animals different from that of humans? (Test yourself 6-1)
Skin covered with fur usually consists of 3 epidermal layers: stratum basale, stratum spinosum, and stratum corneum. A few regions of five-layered epidermis can be found in furry mammals, but these are usually seen in places where the keratinization process has slowed and the skin is very thick The surface of "hairy skin" is covered in scalelike folds. Hair emerges from underneath the scales and is directed away from the opening of the hair follicle. In dogs the hair is organized in clusters of three follicles per scale. Periodically throughout the surface of the epidermis a knoblike elevation can be seen. This is called a tactile elevation, or epidermal papilla. Each tactile elevation is usually associated with a tactile hair. These special hairs are called tylotrich hairs, and they are important in the perception of touch.
ungula
Technical name for hoof
describe the basic anatomy of a bird's beak and claws. when trimming these structures, what should you be careful to avoid? (test yourself 21-1)
The beak consists of an upper and lower mandible. It is covered with a tough, horny keratin layer that grows continuously. Beaks vary in their hardness and flexibility, depending on their function. The claw possesses a horny sheath derived from specialized scales at the end of each toe. Like the beak, it also grows continuously. Species differ in the types of claws they possess, based on their perching habits and method of procuring food. For example, chickens, pheasants, and other ground feeders have short, sharp claws that are used to scratch the ground for food; birds of prey have claws called talons that are long, sharp, and rounded to catch and kill their prey; vultures, which are scavengers, have short, blunt claws; and climbing birds, such as woodpeckers and nuthatches, have strongly curved claws for gripping. When coping beaks and claws, one must be careful to avoid the blood and nerve supply.
what are the four orders of living reptiles? what are the three orders of amphibians? (test yourself 22-1)
The class Reptilia comprises four orders: (1) Crocodylia (alligators and crocodiles), (2) Squamata (snakes and lizards), (3) Chelonian (turtles and tortoises), and (4) Rhynchocephalia (tuataras). The class Amphibia is made up of three orders: (1) Gymnophiona (caecilians), (2) Anura (frogs and toads), and (3) Caudata (salamanders and newts).
what types of feather are flight and tail feathers? describe their microstructure (test yourself 21-2)
The flight and tail feathers are contour feathers (also called remiges on the wings, auriculars around the ear openings, and rectrices on the tail). Contour feathers are moved by muscles attached to the walls of the follicles. The microstructure consists of several structures. The inferior umbilicus is a tiny opening at the base of the feather, where it inserts into the skin. When a new feather is developing, it receives nourishment from blood vessels that pass through this opening. The superior umbilicus is a tiny opening on the feather shaft where the webbed part of the feather begins. In some birds it gives rise to an afterfeather, which is an accessory feather that is thought to provide additional insulation to retain a bird's body heat. The calamus (quill) is the round, hollow, semitransparent portion of a feather that extends from the inferior umbilicus to the superior umbilicus. The rachis is the main feather shaft. The vane is the flattened part of a feather that appears weblike on each side of the rachis. The vane consists of numerous slender, closely spaced barbs. The barbs give rise to barbules, which have rolled edges and tiny hooklets (hamuli). These hooklets interlock each barb with an adjacent one, forming a tightly linked, flexible web. The degree of tightness varies with the species. For example, the contour feathers of owls have fewer barbules than do those of hawks. The result is a looser feather weave that feels softer and allows air to pass through, creating silent flight.
define the function of the uropygial gland. do all birds possess this gland? (test yourself 21-1)
The function of the uropygial (preen) gland is the secretion of an oily, fatty substance that helps to clean and waterproof the feathers. The gland is completely lacking in some parrots, ostriches, and a few other species.
How do the wing and tail feathers differ between predatory and prey bird species? (test yourself 21-2)
The major flight feathers of many prey species are loosely seated in the follicles so that they can drop feathers quickly if grabbed as an aid to escape a predator. In predatory bird species the feathers are seated very strongly in the follicles, and pulling out a flight or tail feather can result in permanent follicle damage, preventing a new feather from ever growing in
what is keratinazation and why is it an important process? (Test yourself 6-1)
The majority of cells in the epidermis are keratinocytes. Keratinocytes located along the basement membrane are well nourished by the blood supply of the underlying dermis; therefore, these cells can grow and divide. When new daughter cells are produced, they push older cells away from the life-sustaining nutrients of the dermis toward the outer layers of the epidermis. As older cells travel from the basal to the superficial layers, they undergo profound changes: they fill with keratohyalin granules; lose their nuclei, cytosol, and organelles; and ultimately become lifeless sheets of keratin. This process is called keratinization and enables millions of dead cells to rub off or "exfoliate" daily at no expense to the animal's health. Keratinization is important because keratin is a tough, fibrous, waterproof protein that gives skin its resiliency and strength
how does hair form and grow? (test yourself 6-3)
The part of hair visible above the skin is called the shaft, and the portion buried within the skin is called the root. A web of sensory nerve endings called the root hair plexus envelops the root, making it an important touch receptor when the hair is bent. Hair is anchored by the hair follicle. The follicle is an invagination of the epidermis that extends from the skin surface to the dermis or, occasionally, the hypodermis. The deepest part of the hair follicle expands to form a hair bulb. At the base of the bulb is a mound of dermal cells called the papilla. The papilla is covered with rapidly dividing epithelial cells called the matrix. These cells are nourished by blood flow from vessels in the underlying papilla, which stimulates much cell division and growth. As cells divide, older cells are pushed upward into the follicle tunnel away from the papilla. These cells become keratinized, and as they lose contact with the nutrition provided by the papilla, they die and become part of the developing hair. In this way, hair is constructed from dead epithelial cells. The wall of a hair follicle is composed of three layers: an internal epithelial root sheath, an outer epithelial root sheath, and a dermal or connective tissue root sheath. Animals with fur often have compound follicles in which multiple hair strands emerge from a single epidermal orifice, or pore, although each strand has its own follicle and bulb. As many as 15 hairs may be associated with one pore. Usually in compound follicles a single long primary hair (also known as a guard hair or cover hair) is surrounded by shorter secondary hairs called satellite hairs. In dogs, usually three compound follicles are grouped together to emerge from the same epidermal fold. Hair is formed in three concentric layers. The innermost layer (and central core) is called the medulla. It is composed of two to three layers of loosely arranged cells that are separated by spaces filled with liquid or air. The cells themselves contain flexible, soft keratin similar to that found in the stratum corneum of the epidermis. Surrounding the medulla is the cortex. Unlike the flexible medulla, the cortex is stiff and rigid because it is composed of hard keratin and is the thickest of the three layers. A single layer of cells arising from the edge of the papilla form the hair surface, the cuticle, which is also composed of hard keratin. The cells of the cuticle are layered like shingles on a roof, which prevents the hairs from sticking together and forming mats. In some animals such as sheep, however, the edges of the cells in the cuticle are raised, enabling them to grab onto the cuticle cells from other hair strands.
what factors stimulate contraction of the arrector pili muscle? why is this muscle important? (test yourself 6-3)
The sympathetic nervous system stimulates the contraction of the arrector pili muscles when an animal is frightened or cold. This reaction is a defense mechanism designed to make the animal appear bigger and therefore less vulnerable to potential predators. In addition, hair that stands erect can better trap insulating layers of air than can nonerect hair, so animals with erect hair coats stay warmer than animals with flat coats. The arrector pili muscle also is responsible for forcing sebum from the sebaceous gland, which helps keep the integument moist and supple.
name two types of sweat gland. how are they different from one another? (test yourself 6-4)
Two types of sweat glands are eccrine and apocrine. The excretory portion of the eccrine gland consists of a simple coiled tube located in the dermis or hypodermis and connected to the surface of the skin by a long duct. In dogs, eccrine sweat glands are found only in the deep layers of the fat and connective tissue of footpads. Like eccrine sweat glands, apocrine sweat glands have a coiled excretory portion buried in the dermis or hypodermis with a single excretory duct. However, unlike eccrine sweat glands, apocrine glands empty into hair follicles rather than onto the surface of the skin. In the dog, apocrine glands are located in the external ear canal.
where are anal sacs found and what is their importance to animals? (test yourself 6-4)
Two types of sweat glands are eccrine and apocrine. The excretory portion of the eccrine gland consists of a simple coiled tube located in the dermis or hypodermis and connected to the surface of the skin by a long duct. In dogs, eccrine sweat glands are found only in the deep layers of the fat and connective tissue of footpads. Like eccrine sweat glands, apocrine sweat glands have a coiled excretory portion buried in the dermis or hypodermis with a single excretory duct. However, unlike eccrine sweat glands, apocrine glands empty into hair follicles rather than onto the surface of the skin. In the dog, apocrine glands are located in the external ear canal.
reptilia includes
alligators/crocs snakes/lizards turtle/tortoises tuataras
thin eyelids in some lizards
allows for some vision with eyelids closed
derivatives of skin in birds
beak claws feathers
How does an ectothermic animal maintain an appropriate body temperature? (test yourself 22-1)
behavioral thermoregulation - Movements within the thermal gradient of their habitat as well as postural changes enable herptiles to adjust their body temperatures as needed. For instance, many herptiles bask to elevate body temperatures and seek shade when they need to cool down. A snake trying to conserve body heat coils tightly to decrease surface area and consequently heat loss, whereas a hot snake uncoils to accomplish the opposite. Some animals can actually adjust the color and pattern of their skin to increase or decrease the absorption of thermal energy from the sun (for example, chameleons).
What causes pigmentation of skin? (test yourself 6-2)
caused by the presence or absence of melanin granules in the armlike extensions of the melanocytes. Macroscopically, no pigmentation is apparent if the granules are concentrated around the nucleus in the cell body of the melanocyte. As the granules move into the cellular arms and into the surrounding tissue, however, pigmentation becomes apparent. The more granules that exist in the arms of the melanocyte and surrounding tissue, the darker the pigmentation. The dispersion of granules is controlled by the release of melanocyte-stimulating hormone, which, in turn, is controlled by the intermediate lobe of the hypophysis. The melanosomes are transported to the tips of the cellular projections, where they are released into the intracellular space and ultimately absorbed by keratinocytes, which arrange the melanin on the side of the cell with the greatest amount of sun exposure. In this way, pigment acts to protect cells from the damaging effects of ultraviolet rays.
ectothermic
cold-blooded dependent on envmt to regulate body temp
epidermis
composed of keratinized stratified squamous epithelium and forms outer waterproof shield avascular but provided with nutrients by interstitial fluid that diffuses up from underlying dermis
6 types of feathers on bird's body
contour: most visible. constitute flight and tail feathers semiplume: found under contour feathers. possess main rachis w/ barbs that lack barbules and hooklets. provide insulation and help with buoyancy in water birds down: soft and fluffy. located next to skin under contour feathers. help with insulation filoplume: bare shaft that lacks barbs on majority of length (except tip). located on nape and upper back near contour feathers. follicles contain sensitive nerve endings bristles: modified contour w/ stiff rachis and few barbs at the base powder down: grow continuously at base. birds w/o abundant uropygial gland have abundant powder down feathers
which reptiles have a tapetum? (test yourself 22-3)
crocodiles
each hair strand is organized into 3 layers:
cuticle: hair surface. composed of hard keratin. prevent cells from sticking together and forming mats cortex: hard keratin. surround medulla. stiff and rigid. thickest of 3 layers medulla: flexible. soft kertain. core
stratum germinativum
deepest. single row of keratinocytes firmly attached to epithelial basement membrane and actively engaged in cell division merkel, melanocytes, keratinocytes found here
dermis in reptiles
dense connective tissue contains blood and lymph vessels, nerves, chromatophores
two distinct layers of skin
dermis epidermis (corium) *separated by basement membrane
How is the dermis different from the epidermis? (Test yourself 6-1)
dermis is highly fibrous: composed of dense, irregular connective tissue that contains collagen, elastic, and reticular fibers. Hair follicles, nerve endings, glands, smooth muscle, blood vessels, and lymphatics are all found in the dermis creating a rich and interesting tissue community. Fibroblasts, adipocytes, and macrophages also are present and represent the most commonly found cellular elements. The dermis is a tough layer that binds the superficial epidermis to the underlying tissues. It represents the "hide" of the animal and is used to make leather.
Differentiate between eccrine and apocrine sweat glands.
eccrine: excretory portion consists of simple coiled tube in dermis or hypodermis. connected to skin's surface by long duct apocrine: excretory portion is coiled and buried in ermis or hypodermis with single excretory duct. empty into hair follicles
molting
feather replacement
remiges
flight feathers
stratum lucidum (clear layer)
found only in very thick skin
amphibia includes
frogs/toads salamanders/newts caecilians
Describe the structure and location of sebaceous glands.
generally found all over body except in specialized regions (like paw pads and planum nasale) located in dermis. simple or complex alveolar structures most have single duct that empties into hair follicle while others empty directly onto skin's surface lined with epithelial cells that manufacture and store oily, lipid substance (glycerides and free fatty acids)
tactile hairs
important for perception of touch
mange
inflammation of dermis and epidermis caused by tiny mites that live in or on the skin noteoedres is most common linked to mange in dogs and cats
skin of reptiles
keratinized integument: subQ space, dermis, epidermis scales
List the cell types that comprise the epidermis and describe the function of each cell type
keratinocytes: majority. produce keratin (resiliency & strength). can grow and divide. involved in keratinization (enables dead cells to rub off daily) melanocytes: pigment of skin (melanin). protection against exposure to UV rays merkel cells: small #s. associated w/ sensory nerve ending (and touch sensation) langerhans cells: macrophages. originates in bone marrow and migrates to skin where it phagocytosizes microinvaders and helps stimulate aspects of immune system
most reptiles possess both ___ and___ glands
lacrimal harderian
List the structures that comprise the hypodermis
loose layer of areolar tissue rich with adipose, blood, and lymphatic vessels, and nerves. permits the skin to move freely over underlying bone and muscle without putting tension on the skin that would result in tearing. pacinian corpuscle: touch receptors sensitive to heavier pressure
stratum granulosum (granular layer)
middle layer 2-4 layers flattened, diamond-shaped keratinocytes glycolipids play important role in waterproofing skin cell dies here
spectacle/brille
modified scales covering eyes (snakes)
do birds have sweat glands?
no
stratum corneum (horny layer)
outermost layer up to 3/4 of epidermis thickness 20-30 rows keratinocytes "dandruff"
List the structures that comprise the dermis and describe the function of each.
papillary layer: just beneath epithelial layer. composed of loose connective tissue w/ loosely woven fibers and ground substance. dermal papillae help to cement dermis and epidermis together. blood vessels provide nourishment to active cells in stratum basale. meissner's corpuscles (nerve endings or pain receptors) reticular layer: dense, irregular connective tissue. 80% of dermis. tension lines indicate separation between fibrous bundles
Describe the unique features of the paw pads and planum nasale
paw pads: thick layers of fat and connective tissue for protection against abrasion and thermal variation. outer surface is thickest and toughest skin on body. - 5 epidermal layers. minute conical papillae cover entire pad. exocrine sweat glands and lamellar corpuscles planum nasale (top of the nose): composed of polygonal plates packed together. - 3 epidermal layers in dogs (lacking stratum lucidum and granulosum). corneum has 4-8 cell layers. contains no glands in epidermis or dermis
uropygial gland
preen gland in birds located at base of tail
pigmentation is caused by
presence of melanin granules
subQ space in reptiles
relatively inelastic
dewclaws
remains of digits that have regressed in the course of evolution
herptiles
reptiles and amphibians
anal sacs
scent glands located at 5 & 7 o'clock relative to anus lined with sebaceous and apocrine glands
corium
sensitive tissue that claws and hooves rest on
stratum spinosum (spiny layer)
several layers of cells held together by desmosomes langerhans cells found in greater abundance where slender projections form weblike frame around keratinocytes
ecdysis
shedding of skin in response to growth or injury
List the five layers of the epidermis.
stratum germinativum (deepest) stratum spinosum stratum granulosum stratum lucidum stratum corneum (outermost)
retrices
tail feathers
feak
the action of wiping the beak in order to remove fragments of food and feathers
beaks vary in hardness and flexibility depending on
their function
nictitans
third eyelid
Ecdysis in reptiles is under the control of what hormone? (test yourself 22-2)
thyroid hormone
coping of beaks and nails
trimming or reshaping
extraocular muscles in reptiles
usually poorly developed chameleon is exception