Utilization of food by the body
There is plenty of venison in market. Fatty acids found in the human diet and in body tissues range from a chain length of 4 carbons to 22 or more, each chain having an even number of carbon atoms. A student pursuing two majors must meet all the degree requirements of one major and at least the departmental requirements of the other. Trans fats are chemical lipids not food found in nature. The General Education program develops analytical and critical thinking skills and the ability to make reasoned judgments. Develop an understanding of behavioral, political, economic, and social systems.
The epidermis helps the skin to regulate body temperature. Epidermis is divided into several layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and are sloughed off, or desquamated.
This process is called keratinization and takes place within weeks. The outermost layer of the epidermis consists of 25 to 30 layers of dead cells. Blood capillaries are found beneath the epidermis, and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips. There are less than genes that are specific for the skin and these are expressed in the epidermis. The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain.
The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many nerve endings that provide the sense of touch and heat. It contains the hair follicles , sweat glands , sebaceous glands , apocrine glands , lymphatic vessels and blood vessels.
The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the Stratum basale of the epidermis. The dermis is structurally divided into two areas: The papillary region is composed of loose areolar connective tissue. It is named for its fingerlike projections called papillae , that extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin.
In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These epidermal ridges occur in patterns see: The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous , elastic , and reticular fibers that weave throughout it. These protein fibers give the dermis its properties of strength, extensibility, and elasticity.
Also located within the reticular region are the roots of the hairs , sebaceous glands , sweat glands , receptors , nails , and blood vessels. Tattoo ink is held in the dermis. Stretch marks often from pregnancy and obesity , are also located in the dermis. The subcutaneous tissue also hypodermis and subcutis is not part of the skin, and lies below the dermis of the cutis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves.
It consists of loose connective tissue, adipose tissue and elastin. Fat serves as padding and insulation for the body. Human skin shows high skin color variety from the darkest brown to the lightest pinkish-white hues. Human skin shows higher variation in color than any other single mammalian species and is the result of natural selection.
Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation UVR penetrating the skin, controlling its biochemical effects. The actual skin color of different humans is affected by many substances, although the single most important substance determining human skin color is the pigment melanin.
Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans.
The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or the stimulation of the nervous system anger, fear , arterioles dilate.
There are at least five different pigments that determine the color of the skin. There is a correlation between the geographic distribution of UV radiation UVR and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator.
Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations. In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males.
Females need more calcium during pregnancy and lactation , and vitamin D which is synthesized from sunlight helps in absorbing calcium. For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium. The Fitzpatrick scale   is a numerical classification schema for human skin color developed in as a way to classify the typical response of different types of skin to ultraviolet UV light:.
As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages. Among other things, skin aging is noted by a decrease in volume and elasticity. There are many internal and external causes to skin aging.
For example, aging skin receives less blood flow and lower glandular activity. A validated comprehensive grading scale has categorized the clinical findings of skin aging as laxity sagging , rhytids wrinkles , and the various facets of photoaging, including erythema redness , and telangiectasia , dyspigmentation brown discoloration , solar elastosis yellowing , keratoses abnormal growths and poor texture.
Cortisol causes degradation of collagen ,  accelerating skin aging. Anti-aging supplements are used to treat skin aging. Photoaging has two main concerns: In younger skin, sun damage will heal faster since the cells in the epidermis have a faster turnover rate, while in the older population the skin becomes thinner and the epidermis turnover rate for cell repair is lower which may result in the dermis layer being damaged. The human skin is a rich environment for microbes. Most come from only four phyla: Propionibacteria and Staphylococci species were the main species in sebaceous areas.
There are three main ecological areas: In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture of species but dominated by b- Proteobacteria and Flavobacteriales. Ecologically, sebaceous areas had greater species richness than moist and dry ones. The areas with least similarity between people in species were the spaces between fingers , the spaces between toes , axillae , and umbilical cord stump.
Most similarly were beside the nostril , nares inside the nostril , and on the back. Reflecting upon the diversity of the human skin researchers on the human skin microbiome have observed: The NIH has launched the Human Microbiome Project to characterize the human microbiota which includes that on the skin and the role of this microbiome in health and disease. Microorganisms like Staphylococcus epidermidis colonize the skin surface.
The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings. Diseases of the skin include skin infections and skin neoplasms including skin cancer. Dermatology is the branch of medicine that deals with conditions of the skin. The skin supports its own ecosystems of microorganisms , including yeasts and bacteria, which cannot be removed by any amount of cleaning.
Estimates place the number of individual bacteria on the surface of one square inch 6. Oily surfaces, such as the face, may contain over million bacteria per square inch 6. Despite these vast quantities, all of the bacteria found on the skin's surface would fit into a volume the size of a pea.
When the balance is disturbed, there may be an overgrowth and infection, such as when antibiotics kill microbes , resulting in an overgrowth of yeast. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of microbes.
Cosmetics should be used carefully on the skin because these may cause allergic reactions. Each season requires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy. Oily skin is caused by over-active sebaceous glands, that produce a substance called sebum , a naturally healthy skin lubricant.
Oily skin is typified by shininess, blemishes and pimples. The negative aspect of the oily-skin type is that oily complexions are especially susceptible to clogged pores, blackheads , and buildup of dead skin cells on the surface of the skin. Human skin has a low permeability ; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles.
However, in some cases it is desirable to allow particles entry to the body through the skin. Potential medical applications of such particle transfer has prompted developments in nanomedicine and biology to increase skin permeability. One application of transcutaneous particle delivery could be to locate and treat cancer. Nanomedical researchers seek to target the epidermis and other layers of active cell division where nanoparticles can interact directly with cells that have lost their growth-control mechanisms cancer cells.
Such direct interaction could be used to more accurately diagnose properties of specific tumors or to treat them by delivering drugs with cellular specificity. The permeability of skin relative to different shapes of nanoparticles has also been studied.
Research has shown that spherical particles have a better ability to penetrate the skin compared to oblong ellipsoidal particles because spheres are symmetric in all three spatial dimensions. Titanium oxide TiO2 , zinc oxide ZnO , and silver nanoparticles are ineffective in penetrating the skin past the stratum corneum.
Because CdSe is toxic to living organisms, the particle must be covered in a surface group. An experiment comparing the permeability of quantum dots coated in polyethylene glycol PEG , PEG- amine , and carboxylic acid concluded the PEG and PEG-amine surface groups allowed for the greatest penetration of particles.
The carboxylic acid coated particles did not penetrate past the stratum corneum. Scientists previously believed that the skin was an effective barrier to inorganic particles.
Damage from mechanical stressors was believed to be the only way to increase its permeability. For example, ultraviolet radiation UVR has been used to slightly damage the surface of skin, causing a time-dependent defect allowing easier penetration of nanoparticles. When the TEWL reaches its highest value, the maximum density of nanoparticles is able to permeate the skin. Studies confirm that UVR damaged skin significantly increases the permeability.
However, the specific permeability of skin after UVR exposure relative to particles of different sizes and materials has not been determined. Other skin damaging methods used to increase nanoparticle penetration include tape stripping, skin abrasion , and chemical enhancement. Tape stripping is the process in which tape is applied to skin then lifted to remove the top layer of skin.
Skin abrasion is done by shaving the top micrometers off the surface of the skin. Chemical enhancement is the process in which chemicals such as polyvinylpyrrolidone PVP , dimethyl sulfoxide DMSO , and oleic acid are applied to the surface of the skin to increase permeability.
Electroporation is the application of short pulses of electric fields on skin and has proven to increase skin permeability. The dietary lysine requirement during the early starter phase is quite high 1.
The requirement continues to decrease throughout the growing-finishing stage from 1. The amino acids of greatest practical importance in diet formulation ie, those most likely to be at deficient levels are lysine, tryptophan, threonine, and methionine.
Corn, the basic grain in most swine diets, is markedly deficient in lysine and tryptophan. The other principal grains for pigs grain sorghum, barley, and wheat are low in lysine and threonine.
The first limiting amino acid in soybean meal is methionine, but sufficient amounts are provided when soybean meal is combined with cereal grains into a complete diet that meets the lysine requirement. An exception might be in young pigs that consume diets with high levels of soybean meal or diets containing dried blood products low in the sulfur-amino acids.
Milk protein is well balanced in essential amino acids but usually is too expensive to be used in swine diets, except for very young pigs. Dried whey, commonly used in starter diets, contains protein with an excellent profile of amino acids, but the total protein content of whey is low.
Diets based on corn and animal-protein byproducts eg, meat meal, meat and bone meal are inferior to corn-soybean meal diets, but they can be improved significantly by adding tryptophan or supplements that are good sources of tryptophan. Animal proteins are also good sources of minerals and B-complex vitamins.
Diets formulated for early weaned pigs that contain high levels of dried animal plasma or dried blood cells may be deficient in methionine. However, high levels of methionine can depress growth, so methionine should not be added indiscriminately to diets. Supplemental valine may be of value in corn-soybean meal diets fed to lactating sows, but it is still too expensive to be considered as a dietary supplement. Lysine is generally the first limiting amino acid in almost all practical diets, so if diets are formulated on a lysine basis, the other amino acid requirements should be met.
A general rule of thumb is that crude protein content can be reduced by 2 percentage points and the diet supplemented with 0. Additionally, it is becoming more popular to formulate swine diets on the basis of standardized or true or apparent digestible amino acids.
This method is particularly advantageous when substantial amounts of byproduct feeds are included in the diet. These nutritional elements have many important functions in the body. Although used primarily in skeletal growth, calcium and phosphorus play important metabolic roles in the body and are essential for all stages of growth, gestation, and lactation. The NRC estimates requirements of 0. The requirements are higher for younger pigs and lower for finishing pigs, but the ratios of calcium: These levels are adequate for maximal growth rate and efficiency of gain , but they do not allow for maximal bone mineralization.
Generally, maximal bone ash and strength can be achieved by including 0. For gestating and lactating sows, calcium and phosphorus requirements are influenced by stage of gestation the first 90 days versus the final 25 days of gestation , parity, milk production, and other factors see Table: The higher requirements during late gestation are attributed to rapid development of the fetuses.
Swine producers may choose to feed slightly higher levels to sows to ensure adequacy of these minerals and to prevent posterior paralysis in heavy milking sows. The calcium and phosphorus requirements listed are based on daily feed intakes of 4. If less feed is consumed per day, the percentages of calcium and phosphorus may need to be adjusted upward.
The ratio of total calcium: The ratio is less critical if the diet contains excess phosphorus. When based on digestible phosphorus, the ideal ratio of calcium to digestible phosphorus is between 2: Most of the phosphorus in cereal grains and oilseed meals is in the form of phytic acid organically bound phosphorus and is poorly available to pigs, whereas the phosphorus in protein sources of animal origin, such as meat meal, meat and bone meal, and fish meal, is in inorganic form and is highly available to pigs.
Even in cereal grains, availability of phosphorus varies. ATTD phosphorus represents the phosphorus digested, and STTD phosphorus is the digestible phosphorus corrected for endogenous phosphorus excretions. Phosphorus supplements such as monocalcium or dicalcium phosphate, defluorinated phosphate, and steamed bone meal are excellent sources of highly available phosphorus.
These supplements also are good sources of calcium. Ground limestone also is an excellent source of calcium. Phosphorus is considered a potential environmental pollutant, so many swine producers feed diets with less excess phosphorus than in the past to reduce phosphorus excretion. Supplemental phytase, an enzyme that degrades some of the phytic acid in feedstuffs, is commonly added to diets to further reduce phosphorus excretion.
The general recommendation is that dietary calcium and phosphorus can both be reduced by 0. The recommended level of salt is 0. Animal, fish, and milk byproducts can contribute some of the sodium and chloride requirement.
Practical diets contain ample amounts of these minerals from the grain and protein sources, and supplemental sources are not needed. Magnesium oxide supplementation has been used to prevent cannibalism, but controlled studies do not support this practice. These minerals are involved in many enzyme systems.
Both are necessary for formation of Hgb and, therefore, for prevention of nutritional anemia. Because the amount of iron in milk is very low, suckling pigs should receive supplemental iron, preferably by IM injection of — mg in the form of iron dextran, iron dextrin, or gleptoferron during the first 3 days of life also see Iron Toxicity in Newborn Pigs.
Giving oral or injectable iron and copper to sows will not increase piglet stores at birth nor will it increase the iron in colostrum and milk sufficiently to prevent anemia in neonatal pigs. High levels of iron in lactation feed results in iron-rich sow feces that pigs can obtain from the pen. Iron can also be supplied by mixing ferric ammonium citrate with water in a piglet waterer or by frequently placing a mixture of iron sulfate and a carrier, such as ground corn, on the floor of the farrowing stall.
The copper requirement for growing pigs is low 3—6 ppm but higher for sows. The estimated copper requirement of 5 ppm for sows in the previous NRC publication was increased to 10 ppm for gestation and 20 ppm for lactation in the edition. The action of copper at high levels appears to be independent of, and additive to, the growth-stimulating effect of antibiotics. Copper sulfate at high levels in the diet results in very dark-colored feces.
Also, high copper diets result in marked increases in the copper content of excreted manure. The thyroid gland uses iodine to produce thyroxine, which affects cell activity and metabolic rate. The iodine requirement of all classes of pigs is 0.
Stabilized iodized salt contains 0. Although essential for normal reproduction and growth, the quantitative requirement for manganese is not well defined. Zinc is an important trace mineral with many biologic functions. Grain-soybean meal diets must contain supplemental zinc to prevent parakeratosis see Parakeratosis.
Higher levels of zinc may be needed when dietary calcium is excessive, especially in diets typically high in phytic acid such as corn-soybean meal diets. In some instances, high levels of zinc oxide have been reported to reduce the incidence and severity of postweaning diarrhea.
Responses to zinc oxide and antibiotics seem to be additive in nature, much like the responses to high copper and antibiotics; however, there is no advantage to including high copper and high zinc in the same diet. Similar to copper, high levels of dietary zinc cause increased zinc content in the excreted manure. For sows, the estimated zinc requirement was increased from 50 ppm in the previous NRC publication to ppm in the edition. The selenium content of soils and, ultimately, crops is quite variable.
In the USA, areas west of the Mississippi River generally contain higher amounts of selenium, whereas areas east of the river tend to yield crops deficient in selenium. Under most practical conditions, 0. This trace mineral is regulated by the FDA, and the maximal amount of selenium that can be added to swine diets is 0.
This trace mineral, which is a cofactor with insulin, is required by pigs, but the quantitative requirement has not been established. Cobalt is present in the vitamin B 12 molecule and has no benefit when added to swine diets in the elemental form. These micronutrients serve many important roles in the body. This fat-soluble vitamin is essential for vision, reproduction, growth and maintenance of epithelial tissue, and mucous secretions. Vitamin A is found as carotenoid precursors in green plant material and yellow corn.
The NRC suggests that for pigs, 1 mg of chemically determined carotene in corn or a corn-soybean mixture is equal to IU of vitamin A. The use of stabilized vitamin A is common in manufactured feeds and in vitamin supplements or premixes.
Concentrates containing natural vitamin A fish oils most often may be used to fortify diets. For these reasons, natural feedstuffs probably should not be entirely relied on as sources of vitamin A, especially because synthetic vitamin A is very inexpensive. An international unit of vitamin A is equivalent to 0.
This antirachitic, fat-soluble vitamin is necessary for proper bone growth and ossification. Vitamin D occurs as the precursor sterols, ergocalciferol vitamin D 2 and cholecalciferol vitamin D 3 , which are converted to active vitamin D by UV radiation. Although pigs can use vitamin D 2 irradiated plant sterol or vitamin D 3 irradiated animal sterol , they seem to preferentially use D 3.
Some of the vitamin D requirement can be met by exposing pigs to direct sunlight for a short period each day. Sources of vitamin D include irradiated yeast, sun-cured hays, activated plant or animal sterols, fish oils, and vitamin premixes. For this vitamin, 1 IU is equivalent to 0. This fat-soluble vitamin serves as a natural antioxidant in feedstuffs. Vitamin E is required by pigs of all ages and is closely interrelated with selenium.
Some nutritionists recommend higher dietary levels for sows in the eastern corn belt of the USA, where selenium levels in feeds are likely to be low. Vitamin E supplementation can only partially obviate a selenium deficiency. Green forage, legume hays and meals, cereal grains, and especially the germ of cereal grains contain appreciable amounts of vitamin E.
Activity of vitamin E is reduced in feedstuffs when exposed to heat, high-moisture conditions, rancid fat, organic acids, and high levels of certain trace elements.