User:Daeshag/sandbox

= Dolphin: =

Integumentary System
The integumentary system is an organ system mostly consisted of skin, hair, nails and endocrine glands. The skin of dolphins is very important as it specialized to satisfy specific requirements. Some of this requirements include protection, fat storage, heat regulation, and sensory perception. The skin of a dolphin is made up of 2 parts: the epidermis and the blubber, which consists of two layers including the dermis and subcutis.

The dolphin's skin is known to have a smooth rubber texture and is without hair and glands, except mammary glands. At birth, newborn dolphins have hairs lined up in a single band on both sides of the rostrum, which is their jaw, and usually have a total length of 16-17 cm.

Dolphins are a part of the species Cetacea. The epidermis of this species is characterized by the lack of keratin and by a prominent intertwine of epidermal rete pegs and long dermal papillae. The epidermal rete pegs are the epithelial extensions that project into the underlying connective tissue in both skin and mucous membranes. The dermal papillae are finger-like projections that help adhesion between the epidermal and dermal layers, as well as providing a larger surface area to nourish the epidermal layer. The thickness of a dolphin's epidermis differs, depending on species and age.

Blubber
Blubber is found within the dermis and subcutis layer. The dermis blends gradually with the adipose layer, which is known as fat, because the fat may extend up to the epidermis border and collagen fiber bundles extend throughout the whole subcutaneous blubber which is fat found under the skin. The thickness of the subcutaneous blubber or fat depends on the dolphin's health, development, location, reproductive state and how well it feeds. This fat is thickest on the dolphin's back and belly. Most of the dolphin's body fat is accumulated in a thick layer of blubber. Blubber differs from fat in that, in addition to fat cells, it contains a fibrous network of connective tissue.

The blubber functions to streamline the body and to form specialized locomotor structures such as the dorsal fin, propulsive fluke blades and caudal keels. There are many nerve endings that resemble small, onion-like configurations that are present in the superficial portion of the dermis. Mechanoreceptors are found within the interlocks of the epidermis with dermal ridges. There are nerve fibers in the dermis that extend to the epidermis. These nerve endings are known to be highly proprioceptive, which explains sensory perception. Proprioception, which is also known as kinesthesia, is the body's ability to sense its location, movements and actions. Dolphins are sensitive to vibrations and small pressure changes.

Blood vessels and nerve endings can be found within the dermis. There is a plexus of parallel running arteries and veins in the dorsal fin, fluke and flippers. The blubber manipulates the blood vessels to help the dolphin stay warm. When the temperature drops, the blubber constricts the blood vessels to reduce blood flow in the dolphin. This allows the dolphin to spend less energy heating its own body, ultimately keeping the animal warmer without burning energy as quick. In order to release heat, the heat must pass the blubber layer. There are thermal windows that lack blubber, are not fully insulated and are somewhat thin and highly vascularized, including the dorsal fin, flukes, and flippers. These thermal windows are a good way for dolphins to get rid of excess heat if overheating. Additionally in order to conserve heat, dolphins use countercurrent heat exchange. Blood flows in different directions in order for heat to transfer across membranes. Heat from warm blood leaving the heart will heat up the cold blood that is headed back to the heart from the extremities, meaning that the heart always has warm blood and it decreases the heat lost to the water in those thermal windows.