Individual differences |
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|A. Epidermis B. Dermis
D. Blood and Lymph Vessels E. Stratum Germinativum
1. Hair Shaft 2. Stratum Corneum 3. Pigment Layer 4. Stratum Spinosum 5. Stratum Basale 6. Arrector Pili Muscle 7. Sebaceous Gland 8. Hair Follicle 9. Papilla of Hair 10. Nerve Fiber 11. Sweat Gland 12. Pacinian Corpuscle 13. Artery 14. Vein 15. Sensory Nerve ending (for touch) 16. Dermal Papillary 17. Sweat Pore
This cell is also used to supervise the outer skin from burns and other such articulates.
The hypodermis is used mainly for fat storage.
A layer of tissue that lies immediately below the dermis of vertebrate skin. It is often referred to as subcutaneous tissue though this is a less precise and anatomically inaccurate term. The hypodermis consists primarily of loose connective tissue and lobules of fat. It contains larger blood vessels and nerves than those found in the dermis.
Specifically, the hypodermis contains:
- Loosely arranged elastic fibers
- Fibrous bands anchoring the skin to the deep fascia
- Fat, except in the eyelid, scrotum, penis, nipple and areola
- Blood vessels on route to the dermis
- Lymphatic vessels on route from dermis
- Hair follicle roots
- The glandular part of some sudiferous glands
- Nerves: free endings and Pacinian corpuscles
- Bursae, in the space overlying joints in order to facilitate smooth passage of overlying skin
- Fine, flat sheets of muscle, in certain locations, including the scalp, face, hand, nipple, and scrotum, called the panniculus carnosus
In some animals, such as whales and hibernating mammals, the hypodermis forms an important insulating layer and/or food store.
In some plants, the hypodermis is a layer of cells immediately below the epidermis of leaves. It is often mechanically strengthened, for example, in pine leaves, forming an extra protective layer or a water storage tissue.
According to the eighth edition of Developmental Biology by Scott F. Gilbert, the hypodermis of C. elegans is derived from ectoderm.
Subcutaneous fat is found just beneath the skin as opposed to visceral fat which is found in the peritoneal cavity. Subcutaneous fat can be measured using body fat calipers giving a rough estimate of total body adiposity. This fat aids in the process of homeostasis, by forming a layer of insulation to slow heat loss.
Hypothetical function during human evolutionEdit
Body fat is cited within the aquatic ape hypothesis as the result of adaptation to aquatic environments, as a means of streamlining and insulation. Others have pointed out in response that the subcutaneous fat distribution in humans is more similar to a domesticated animal than an aquatic one, and is nearly identical to that of other primates. The subcutaneous fat of aquatic mammals and humans also seems to serve different uses - it forms the streamlined shape of seals, while in humans it is used for sexual selection; humans display considerable sexual dimorphism in their fat distribution, which is not explained by the aquatic ape hypothesis.
- ↑ Morgan, Elaine (1997). The Aquatic Ape Hypothesis, Souvenir Press.
- ↑ Pond, C (1998). The Fats of Life, 236-8, Cambridge University Press.
- ↑ Adams, C Did humans descend from "aquatic apes"?. The Straight Dope. URL accessed on 2009-08-27.
- ↑ Moore, J Fat and the AAT/H. URL accessed on 2009-09-03.
- ↑ Laden, G Musings on the Aquatic Ape Theory. ScienceBlogs. URL accessed on 2009-09-02.
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