Lecture 7: Anatomy Of The Integuement Part 2

Question 1

What developments did the amphibian make to become terrestrial?

Answer 1

• Started to develop the true stratum corneum
• A more vascular dermis for increased gas exchange
• Development of integuementary glands. (Probably first Salamanders developed unicellular mucous glands, Multicellular Mucous Glands, Multicellular granular (poisonous) glands)

Question 2

Describe the stratum corneum and dermis of amphibians

Answer 2

Stratum Corneum: Amphibians were among the first to get keratinized skin. As a reminder, the keratin comes from the stratum basale and are derived from a protein called eleidin.
Dermis: Well vascularized to provide the amphibian with gas exchange. Some amphibians use this and lungs, some just strictly use dermal gas exchange.

Question 3

What types of glands are found in the amphibian integuement?

Answer 3

• Unicellular glands of Leydig are mucous glands found in certain larval salamanders.
• Multicellular mucous glands are common in the amphibian integument and serve to secrete a water-retaining layer of mucous on the surface of the epidermis.
• Multicellular granular (poison) glands are found in most amphibians and are especially well developed in toads (parotid glands) and in the poison dart frogs, some of which are brightly patterned members of the family Dendrobatidae.

Question 4

How does the reptilian integuement compare with the amphibian integuement (considering adaption and terrestrialism)

Answer 4

• Stratum Corneum is way more developed in reptiles (necessary for water loss and increased epidermal glands)
• The advanced stratum corneum allowed for the growth and development of scales (folds in the corneum) in reptiles.
• The epidermis must be “shed” or “molted” in order for the reptile to continue to grow. Also a staple of the features of the stratum corneum.

Question 5

Describe the epidermal scales on reptiles

Answer 5

• Epidermal scales are derived from the epidermis. (No shit.) So they’re less bone-like than their dermal counterparts. They are interconnected by thin bridges of epidermal skin, which can be removed through shedding.
• These scales can harden and thicken into cornified scales called scutes.

Question 6

Describe reptilian dermal scales

Answer 6

• In turtles, developed dermal scales contribute to the formation of plastron and carapace. These can be overlapped and strengthened with epidermal scales.
• Some lizards have dermal scales called osteoderms.
• Crocodiles have gastralia, which is a fancy name for ventral dermal plates on their surface. (Crocodiles can also have dermal plates on their back)

Question 7

Describe the integument structure of birds.

Answer 7

• Birds have thin skin, but a well developed stratum corneum.
• Glands are overall smaller, one of them, the uropygial gland secretes oil that birds spread all over their feathers to keep them soft and water-proof (this is called preening)
• There are 3 types of bird feathers. The contour feather, the down feather, and the filoplume.

Question 8

Describe the structure of the contour feather.

Answer 8

• Starts off with that stem/shaft looking thing called the Calamus.
• The rest of the stem where it’s all branched is the rachis.
• Barbs extend out of the rachis, and are equipped with hooks and barbules, which connect with adjacent barbs.
• The vane (this part’s weird) consists of the wide flat surface of the barbs connected to the rachus. (Sounds almost like it’s just a perspective thing)

Question 9

Describe features of the contour feather.

Answer 9

• They’re developed in tracts along the skin called pterylae.
• The featherless portions that separate the tracts are called apterylae.
• The feathers in the bird’s forearms and hands (what?) are called remiges. The feathers in the bird’s tail are called retrices.
• The feathers responsible for flight are built into the bones of the wing. The rest of them are just attached to the skin.

Question 10

1. Describe Down Feathers

2. Describe Filoplumes

Answer 10

1. Sometimes called plumules, down feathers are evenly distributed, and are probably ancestral to contour feathers. They have a short calamus, and their barbs are hook-less and are more efficient for trapping air. About as soft and fluffy as Mags.
2. Filoplumes have a threadlike shaft. Filoplumes with a stiffer shaft are called bristles. Bristles can also be used to screen objects from nostrils and increase the effective gape of the mouth, and form eyelashes.

Question 11

Define homeotherms

Answer 11

• Homeotherms are able to maintain a relative constant body temperature in spite of variations in the ambient temperature.
• Homeothermy requires a means of producing heat and a means of either retaining body heat or losing body heat, depending on the ambient temperature. This mostly includes birds and mammals.

Question 12

Describe poikilotherms

Answer 12

• Poikilotherms include fish, amphibians, and reptiles which take on the surrounding ambient temperature.
• Poikilotherms are not “cold blooded,” because they, may have a body temperature that is much higher than that of a homeotherm.
• Poikilotherms typically become sluggish if ambient temperatures drop below optimum operating levels.
• Poikilotherms can employ basking in the sun, body pressing against a warm surface, or shade-seeking in order to alter their body temperature.

Question 13

What are the ways in which homeotherms regulate their body temperature?

Answer 13

• Feathers, Hair, and Fur can trap heat.
• Air is technically an insulator (it is?) and hair and feathers can be raised or lowered autonomously by smooth muscle.
• Natural metabolism is quite high compared to polikilotherms.
• Releasing heat may be accomplished by sweating or panting.
• Blood can rush to the integument (which is where the flushing comes from).

Question 14

Describe the general characteristics of mammalian integument.

Answer 14

• Well developed epidermis and dermis. Hairs are seen for the first time, and is one of mammal’s distinctive characteristic.
• Mammals also have titties. The others don’t really have that. Our dermis is also quite thick, which is why cowhide makes for good leather. It also goes without saying that we don’t really have scales anymore.

Question 15

Describe the human integumentary system

Answer 15

• ## We have thick skin. And thin skin. But this refers to the epidermal complexity. So the thickest skin is actually thin skin, and the thinnest skin (eyelids) is also thin skin. Thick skin is only found on the palms of the hands and the soles of the feet.

Question 16

List the layers of skin from deepest to…um…surfacest.

Answer 16

• Stratum basale (germinativum) (Deepest)
• Stratum spinosum
• Stratum granulosum: (Represented by only a few cells in thin skin)
• Stratum lucidum: (Absent in thin skin)
• Stratum corneum: (Most superficial)

Question 17

List the characteristics of the stratum basale and the stratum corneum

Answer 17

• Stratum basale: Deepest layer, single cell layer, and held together by desmosomes. Hemidesmosomes hold layer to basal lamina. Has a high mitotic activity which produces stem cells differentiating keratinocytes.
• Stratum cornea: Multilayered. 5-50 layers thick. Obviously thicker in thick skin. Enucleated, flattened, dead keratinocytes. Cytoplasm is replaced by keratin.

Question 18

Describe the differences between the dermis and the hypodermis.

Answer 18

Dermis: Dense fibrous irregular connective tissue layer beneath epidermis. Derived from embryonic mesoderm. Induces development of epidermis and epidermal derivatives. Supports epidermis.
Hypodermis: Loose connective tissue that underlies dermis. Corresponds to superficial fascia of gross anatomy. Technically not part of skin. May contain fat cells that can form a thick layer called the panniculus adiposus.

Question 19

What are the two main layers of the dermis?

Answer 19

• Papillary layer (closest to epidermis): Loose CT that is separated from epidermis by basal lamina. Network of fine elastic fibers and abundant capillaries.
• Reticular layer: Dense irregular CT that includes fibrocytes, macrophages, and adipocytes

Question 20

What are the 4 classes of integument derivatives that mammals have?

What are some types of glands mammals possess?

Answer 20

• 1. Glands, 2. Hairs, 3. Claws/Antlers/Hooves/Nails, 4. Chromatophores
• Sudoriferous glands, Sebaceous glands, Mammary glands, Meibomian glands, Glands of Zeiss (eyelids), Ceruminous glands (ears), Scent glands

Question 21

Describe Sudoriferous Glands

Answer 21

Long, hollow, tubular glands, that are generally small in humans, and produce a thin watery secretion (sweat). They can be bigger in other animals. And hairier. The animal versions can be thick and milky.
There’s two types of sweat glands in humans, merocrine sweat glands, which are used to moderate temperature. And apocrine sweat glands. Associated with hair follicles in axillary and pubic region. Bacteria acts upon these sweat glands…for some reason.

Question 22

Describe sebaceous glands, and mammary glands.

Answer 22

• Sebeceous Glands: Holocrine glands, in humans these glands are associated with hair follicles and help to keep the hairs pliable. They may provide a role in waterproofing the integument.
• Mammary Glands: Histologically similar to sudoriferous glands. Both apocrine (fat) and merocrine (proteins) secretion in humans. Monotremes lack teats; glands open directly onto body surface. Human nipples intermediate between the eversion nipple of placentals and the proliferation nipple of ungulates.

Question 23

Describe Hairs in Mammals

Answer 23

Parts of a hair include:

• Shaft of dead, cornified epidermal cells
• Matrix of living, mitotically active tissue that gives rise to the shaft, this matrix is equivalent to the stratum germinativum (basale).
• Multi-layered follicle: Consists of layers derived from both the epidermis and the dermis.
• Vascularized dermal papilla: Provides matrix with oxygen and nutrients. Arrector pilum muscle

Question 24

How are claws, nails, hooves, and horns different from the stratum corneum.

Answer 24

Aside from the obvious that it’s a lot harder, the keratin that makes up these structures (and hairs) has a higher sulfur content than the keratin of the epidermis; it is referred to as hard keratin.

Question 25

Describe the generic structure of hooves, horns, nails, and claws.

Answer 25

The hard, dorsal plate is the ungis. The softer, innervated and vascularized ventral plate is the subungis. A modified layer of the stratum germinativum, the matrix, is found at the proximal end of the ungis. In primates, the nail plate is flattened; in hoofs, the nail plate is curved into the shape of a horseshoe, and in claws, the nail plate is strongly curved or folded.

Question 26

Describe the different stances of animals based on their nail/hoof structure.

Answer 26

• Horses, cattle, and related animals walk on the distal edge of the ungis and, for this reason, are collectively called ungulates and are said to have an Unguligrade stance.
• Members of the cat and dog family and related mammals walk on their toes and are said to have a Digitigrade stance.
• Mammals such as humans and bears walk on the soles of their feet and are referred to as having a plantigrade stance.

Question 27

Describe the horn structure found in the cattle family.

Answer 27

• Hollow structures found in members of the cattle family (bovidae), horns are found in both male and female members of a species and are permanent structures.
• Horns consists of a solid core of bone attached to the frontal bone and covered by a thick layer of stratum corneum.
• The outer epidermis is solidly attached to the bony core.
• In the prong-horned antelope, the outer epidermal core is shed seasonally, but the bony core persists.
• After death, the bony core remains attached to the skull, but the outer stratum corneum becomes detached.

Question 28

Describe the antlers found in the deer (cervidae) family

Answer 28

• Antlers are usually found only in male members of a species (the exception are reindeer, in which both male and female have antlers).
• Antlers are bony outgrowths of the frontal bone.
• The growing bone is covered by a layer of highly vascularized skin called velvet.
• After the antlers are formed, usually just prior to breeding season, the velvet loses its blood supply and becomes dry and is rubbed off.
• After the breeding season, the bony antlers fall off and are re-grown the following year.