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There is keratinization of the epidermis (major feature of the tetrapod integument proper)
-Prominent stratum corneum, which is composed of dead cells filled with water-proofing protein, keratin
-Prevents mechanical abrasion, invasion, etc
Whereas fish glands are in the epidermis, tetrapod glands are generally in the dermis
Amphibian skin in general is different than all other vertebrate skin for what reason?
because, although higher vertebrates do excrete a bit through their skin and use the urinary system, there is more excretion that goes on in the amphibian skin; and, the amphibian skin is also a major structure through which respiration occurs
Explain amphibian skin
the blood vessels supply, particulary the capillary beds, are very numerous - the skin is slightly more complicated
- stratified and cornified in most amphibians; thse that spend most time in water have stratified epithelium with a mucous cuticle
- scattered through the cells of the epidermis, you will find Leydig cells, which secrete substances that resist the entry of bacteria or viruses
- -Stratum spongiosum and compactum
- -Loose and dense irregular
-Dermal scales are really absent, except there are vestiges of dermal scales in certain limbless amphibians
-Contains multicellular glands and lots and lots and lots of blood vessels
Explain nuptial pads
-In many amphibians, during the breeding season, there are nuptial pads that are found in some of the digits of the male; these are really cornified epithelium
Function of nuptial pads
-Function is to grasp on and hold on to the female because, in many amphibians during breeding, the male squeezes the eggs out of the female
Reptilian integument characteristics
- Reptiles have much more keratinization
- There are very few glands in reptilian skin
Epidermis: there are three layers (in to out stratum basale (where cell division takes place), stratum granulosum, stratum corneum (upper layer))
- Dermis: two regions—the spongiosum and the compactum
- –Dermal bone is present in many reptilian dermises
- –Glands that are present in the skin—roles not well understood; usually restricted to certain parts of the body
True or False:
Reptiles have no hypodermis
False: Hypodermis is also present
Epidermis in birds has two layers—a basale and a corneum
Sometimes, there is a transitional layer between the two where the cells are being transformed into keratinized packets
- Dermis has two regions: spongiosum and compactum
- –Rich blood supply; lots of sensory nerve endings; smooth muscle; there are also glands, but they are restricted to certain areas; and this is for flight and feathers (flight feathers)
Most developed--stratified squamous epithelium with many layers
There are also Langerhans cells scattered throughout the stratified squamous; they function in cell-mediated immunity
In some mammalian cells, you find sensory cells for pressure called Merkel cells, responding to pressure (mechanoreceptors)
Explain the layers of the mammalian epidermis.
Inner to outer: stratum basale (germanitium where mitosis is restricted to), stratum spinosum (nuclei start to enlarge; hypertrophy of the cell—dying process, stratum granulosum (where you see prekeratin fibers), stratum lucidum (layer of transparent cells located in soles of feet and palms of hands), stratum corneum
–Dermis is also well developed with double layers, but this time, the dermis projects into the epidermis For that reason, the layer is referred to as the papillary layer= stratum spongiosum
Explain the papillae of the dermis
In these papillae is where you find capillaries—brings blood supply closer to epithelial tissue, which is avascular
Deeper layer of the dermis is?
Deeper layer is the reticular layer (stratum compactum—dense irregular CT and most of the structures of the dermis—blood vessel, nerves, hair, etc. are found here
In terms of dermal bone in mammals?
In terms of dermal bone, it usually contributes to parts of the skull; rarely are there dermal scales
What is underneath the mammalian dermis?
What are specialized hairs in mammals?
There are specialized hair called vibrissae (whiskers) which surround the snout of many mammals
-epidermal derivative, meaning that it comes from the epithelium; you can see the epithelial layer found on the outside of the hair
Even though it originates in the dermis, it is derived from the epidermis
Explain the hair formation
- -It reaches deep down into the dermis to form the hair follicle. At the very base of the follicles an invagination is a papillae; that is where capillaries and nerves are located to control the hair
- -As division takes palce and the cells are pushed up through this hair follicle and pierce the epidermis and then reach the outside, what you are looking at is the shaft—dead keratinized epithelium. By the time the cells reafch the surface, they are dead epithelial tissue. The structure of the keratin in hair is a little bit different than structure of keratin in skin and nails, resulting in a different texture
Associated with hair follicles are __
sebaceous glands and arrector pili muscle
What do sebaceous glansd do
keep hair moist and pliable because they have an oily secretion
What does the arrector pilus do?
- causes hair to stand up on
- -when it contracts, hair stands on end, a reaction to fright or cold