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Animal Anatomy and Physiology: Skin and Teeth
Questions and Answers: The skin
1. Why is skin important and what are the
five functions of skin?
Skin holds all internal structures
in place. Without it, we humans would be mere blobs, with our guts exposed.
“It covers and protects underlying structures and forms a critical
barrier between the delicate inner workings of the body and the harsh
elements of the external world.” (QTD Five functions of skin:
1. Protects what it encloses.
2. Prevents dissication.
3. Is a sensory organ, takes in information from the environment via touch
and pressure and
Conveys this input to regions of the central nervous system.
4. Synthesizes Vitamin D and engages in the storage of nutrients.
5. Stores other nutrients.
6. Assists in the maintenance of normal body temperature and excretes
water, salt, and organic wastes.
2. What is Keratinization?
It’s “the normal formation of keratin (a tough, waterproof
protein) outside epithelial cells of the skin. As the epithelial cells
mature, they fill with granules filled with keratin. It’s an important
process because it enables millions of dead cells to rub off or exfoliate
daily at no expense to the health of the animal. An entirely new epidermis
forms in humans every 7-8 weeks.
3. The five layers of the epidermis and what’s going on in each layer are as follows:
1. Stratum Germinativum. Deepest layer. Also known as the stratum basale or the basal layer. Consists of a single row of keratinocytes, which are firmly attached to the epithelial basement membrane and are actively engaged in cell division. The daughter cells move from the stratum basale to the more superficial laters as they mature to replace epithelial cells thathave exfoliated at the skin’s surface. Merkel cells, melanocytes, and keratinocytes are found in the basal layer.
2. Statum Spinosum or Spiny layer. Called this because when the cells of this epidermal later Are fixed for histological examination, they contract into speculated masses that resemble sea Urchins. These cells are sometimes called prickle cells; however, their celluar projections do not occur naturally, and the cells are normally smooth in situ. Unlike the stratum basale, the stratum Spinosum contains several layers of cells that are held together by desmosomes. Although cell division is dramatic in the statum basale, infrequent divisions are seen in the stratum spinosum. Langerhans cells are found in greater abundance in the spinosum later, where their slender Projections form a weblike frame around the keratinocytes.
3. Stratum Granulosum or granular layer. This is in the middles later of skin, It is composed of two to four layers of flattened, diamond-shaped keratinocytes. The cytoplasm of these cells begin to fill with karatohyaline and lamellated granuales, which in turn leads to the dramatic degeneration of the nucleus and other organelles. Without these vital parts, the cell quickly dies. The lamellated granules contain water proofing glyocolipids 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 the waterproofing the skin and in slowing water loss across the epidermis.
4. Stratum Lucidum or clear layer. Is found in very thick skin, so most skin lacks this later. Microscopically, the stratum lucidum appears as a tanslucent layer composed of a few rows of flattened, dead cells. In this clear later and in the outermost epidermal later, the sticky contents of the keatogranules combine with intracellular tomonfilaments to form keratin fibrils.
5. Stratum Corneum or horny layer. This is the outermost later 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. Viewed in a sagittal section, the keratinocytes have a paper thin, almost Two-dimensional appearance, yet when viewed from above, they appear hexagonal. These are only the reminants of the karatinocyres, because the actual cell died in the stratum granulosum. These reminants are sometimes called horny or cornified cells, but are better known as dandruff.
4. How is the skin of hairy animals different
than that of humas?
The skin of hairy animals is different than that of humans in that skin
covered with fur consists of three epidermal layers rather than five.
These layers are the stratum basale, stratum spinosum and the stratum
corneum. A few regions of five-layered epidermis are found in furry mammals,
But these are usually seen in regions where the keratinization process
has slowed and the skin is very thick .The surface of hairy skin is covered
in scale-like folds. Hair emerges from beneath the scales and is directed
away from the opening. In dogs the hair is organized in clusters of three
follicles per scale.
5. How do the dermis and epidermis differ?
The dermis makes up the greatest portion of the integument and
is responsible for most of the structural strength of the skin. Unlike
the epidermis, which is primarily cellular, the dermis is highly fibrous.
It is composed of dense, irregular connective tissue that contains collegen,
eElastic, and reticular fibers. Hair follicles, nerve endings, glands,
smooth muscles, blood vessls, and lymphatic channels are all found in
the dermis as well, creating a rich and interesting tissue community.
Fibroblasts, adipocytes, and macrophages also are present and represent
the most commonly found cellular elements in the dermis.
Questions and Answers: TheTeeth
1. How do diets differ among herbivores,
carnivores, and omnivores?
To which group would cats, horses, cows, and humans belong? Herbivores
are plant eaters, carnivores are meat eaters, and omnivores are animals
that eat plant material and meat. Cats are carnivores, cows and horses
are herbivores, and humans are omnivores.
2. What are the lower arcade and the upper arcade in reference to teeth? What bones of the skull are associated with each of these? The maxilla and the incisive bones of the skull contain the upper arcade of teeth or the teeth in the upper part of the mouth. The mandible contains the lower arcade of the teeth, or teeth in the lower part of the mouth.
3. What are the four types of teeth? Where
are they located from rostral to caudal?
The incisors are the most rostral teeth of the upper and lower arcade.
The canine teeth (when present) are located at the corners of the incisors.
They are typically longer than the other teeth, and pointed at the tip.
In some species, the canine teeth are large and form tusks. The premolars
are the rostral, cheek teeth, and have some fairly sharp points and surfaces
in carnivorous species. The molars are the caudal cheek teeth and have
larger, flatter occlusal surfaces that are used by all species for grinding.
4.What is meant by lingual, palatal, labial,
and buccal surfaces of the teeth?
Lingual surface. The inner surface of the lower arcade of teeth that faces
toward the tongue. Palatal surface. Inner facing surface of the upper
arcade. Faces the hard palate at the roof of the mouth.
Labial surface. The outer facing surface of the upper and lower arcade
at the front (rostral end) of the mouth. Labial means “pertaining
to lips.
Buccal surface. Outer facing surface more caudal in mouth. (Buccal means
pertaining to cheeks).
5. What are deciduous teeth?
Baby teeth.
6. Why do ruminants have a dental formula
that has a zero after the I and the C?
Because they don’t have any upper incisors or canine teeth.
7. Where are the apex, root, pulp, cementum,
dentin, and enamel of a tooth located? What is the gingivia?
The blood supply and nerve supply enter the apex of the tooth root and
make up the pulp in the center of tooth root and make up the pulp in the
center of the tooth. The dentin surrounding the tooth pulp is more dense
than bone and helps to protect the sensitive pulp. The root of the tooth
is covered by cementum, a hard connective tissue that helps fasten the
tooth securely in a bony socket. The crown of the tooth is covered by
a hard enamel layer, which is the hardest, toughest tissue in the body.
The epithelial tissue that forms the gums around the teeth is referred
to anatomically as the gingiva.
8.What are amylase and lipase? From where
in the mouth do they come? What do they do?
Amylase is an enzyme found in the saliva of omnivores, such as rats and
pigs, but is absent in Carnivores, like dogs and cats. As the name implies,
salivary amylase breaks down amylase, a sugar component of starch. Lipase,
an enzyme that digests lipids (fats) may be found in the saliva of young
animals (calves) while they are nursing or on a high milk diet.
9. What effects do the parasympathetic and
the sympathetic nervous system have on the mouth?
The salivary glands, as well as most of the other glands in the digestive
system, are controlled by The autonomic nervous system. Stimulation of
the parasympathetic part of the of the autonomicnervous system results
in increased salivation. The anticipation of eating can cause parasympathetic
stimulation the salivary flands, resulting in copius saliva production,
or drooling. Sympathetic nervous system stimulation associated with fear,
or inhibition of the parasympathetic nervous system by preanesthetic drugs
like atropine, produces “dry mouth” because of the decrease
in saliva production.
10.What is peristalsis? How does it differ
from segmentation?
Peristalsis is coordinated contraction and relaxation of muscle layers,
resulting in movement of a bolus of food or ingesta along the GI tract.
Segmentation mixes GI tract contents and slows movement through the tract.
Skin and Teeth