Your skin takes on different thickness, color, and texture all over your body. For example, your head contains more hair follicles than anywhere else. But the soles of your feet have none. In addition, the soles of your feet and the palms of your hands are much thicker than skin on other areas of your body. Squamous cells. The outermost layer is continuously shed is called the stratum corneum. Basal cells.
Basal cells are found just under the squamous cells, at the base of the epidermis. Underlying the papillary layer is the much thicker reticular layer. This layer is well vascularized and has a rich sensory and sympathetic nerve supply.
The reticular layer appears reticulated net-like due to a tight meshwork of fibers. Elastin fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated. Collagen injections and Retin-A creams help restore skin turgor by either introducing collagen externally or stimulating blood flow and repair of the dermis, respectively.
The hypodermis also called the subcutaneous layer or superficial fascia is a layer directly below the dermis and serves to connect the skin to the underlying fascia fibrous tissue of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.
The hypodermis is home to most of the fat that concerns people when they are trying to keep their weight under control. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes. This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma. Where the fat is deposited and accumulates within the hypodermis depends on hormones testosterone, estrogen, insulin, glucagon, leptin, and others , as well as genetic factors.
Fat distribution changes as our bodies mature and age. Men tend to accumulate fat in different areas neck, arms, lower back, and abdomen than do women breasts, hips, thighs, and buttocks. The body mass index BMI is often used as a measure of fat, although this measure is, in fact, derived from a mathematical formula that compares body weight mass to height. Therefore, its accuracy as a health indicator can be called into question in individuals who are extremely physically fit. In many animals, there is a pattern of storing excess calories as fat to be used in times when food is not readily available.
In much of the developed world, insufficient exercise coupled with the ready availability and consumption of high-calorie foods have resulted in unwanted accumulations of adipose tissue in many people. Although periodic accumulation of excess fat may have provided an evolutionary advantage to our ancestors, who experienced unpredictable bouts of famine, it is now becoming chronic and considered a major health threat.
Not only is this a problem for the individuals affected, but it also has a severe impact on our healthcare system. Changes in lifestyle, specifically in diet and exercise, are the best ways to control body fat accumulation, especially when it reaches levels that increase the risk of heart disease and diabetes. Skip to main content. Chapter 5: The Integumentary System.
Search for:. Layers of the Skin Layers of the Skin Learning Objectives Identify the components of the integumentary system Describe the layers of the skin and the functions of each layer Identify and describe the hypodermis and deep fascia Describe the role of keratinocytes and their life cycle Describe the role of melanocytes in skin pigmentation. The cells in all of the layers except the stratum basale are called keratinocytes.
This layer contains fibroblasts, macrophages and fat cells. The arteries supplying the skin are deep in the hypdermis. Branches from the arteries pass upwards to form a deep and a superficial plexus. It supplies the fatty tissue of the hypodermis, and the deeper parts of the dermis, including the capillaries for hair follicles, deep sebaceous glands and sweat glands.
The superficial subpapillary plexus lies just beneath the dermal papillae, and supplies the capillaries in the dermal papillae. The pink colour of skin is mainly due to the blood seen in venules of this plexus. There are many arteriovenous anastomoses in the dermis, which can prevent blood from entering the superficial cutaneous plexus.
This strategy is used as a response to cold as a way of conserving heat. The danger is that if the epidermis loses its blood supply for too long, it will die frostbite! Alternatively, when it is hot, more blood is allowed into the superficial plexus, and the skin flushes. The blood in the superficial capillaries is cooled by the evaporation of sweat of the surface of skin. Skin functions and Layers Some facts about skin Skin is the largest organ of the body. It has an area of 2 square metres 22 square feet in adults, and weighs about 5 kilograms.
The thickness of skin varies from 0. Skin is the major barrier between the inside and outside of your body! Functions of skin Protection : it protects against UV light, mechanical, thermal and chemical stresses, dehydration and invasion by micro-organisms.
Sensation : skin has receptors that sense touch, pressure, pain and temperature. Thermoregulation : various features of the skin are involved in regulating temperature of the body. For example sweat glands, hair, and adipose tissue. Metabolic functions : subcutaneous adipose tissue is involved in production of vitamin D, and triglycerides.
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