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During all the centuries of whaling the blue whale has been one of the few species that could not be caught in sufficient number to make its taking commercially profitable. The species was too powerful, too huge, and too swift in its movements for antiquated whaling equipment and methods. With the exception of the ventral surfaces of the pectoral fins, which are white, the entire body and appendages of this whale are one color, namely, blue-gray. However, the animal frequently passes through areas of water full of a plankton growth that colors the dermis a yellow hue; it may be that this is the condition that gave rise to the incorrect American name; but if the carcass is carefully examined under such circumstances it will be found that the yellow covering can be easily scraped off, exposing the normal blue-gray color of the dermis.

Skin is a specialized boundary tissue which forms the entire external surface of the body and is continuous with mucosa lining the respiratory, gastrointestinal, and urinogenital tracts at their respective openings. Skin is the largest organ in the body but is often overlookedin this respect. Skin has many functions, some of which are not immediately obvious. • It minimizes damage from mechanical, thermal, osmotic, chemical, and sunlight insults. • It forms a barrier against microorganisms. • It has a major function in thermoregulation. • It is a sensory surface equipped with touch, pressure, temperature, and pain receptors. • It has good frictional properties useful in locomotion and handling objects. • It is waterproof. • It is the site of vitamin D synthesis. • It also plays a role in non-verbal communication when we blush, alter our facial expression, or use tactile communication such as touching or kissing.Skin has two distinct parts when seen under a microscope, the superficial epidermis and the deeper dermis. The epidermis is a surface epitheliumin which the outer cells are keratinized. Keratinization is the deposition of tough mats of keratin which are intracellular fibrous proteins that make the cells tough; keratinization also kills the superficial cells so the outer layers of your skin are dead. The epidermis varies in thickness. The thickest and most heavily keratinized areas are on the soles of the feet and palms of the hands whereas the epidermis on the face and back of the hand is much thinner and less heavily keratinized. Habitual activity, such as holding a pen, digging with a shovel or using scissors, may produce localized thickenings of thick skin by increasing the thickness of keratin to produce calluses. Cells below the keratin layer have a special coating that forms a permeability barrier, preventing water moving between cells, thus preventing water loss from the body and water-logging when exposed to water. Epithelium does not contain blood vessels, which is why you do not bleed when you lightly knock your skin. To bleed, you need to expose the blood vessels that lie in the dermis and supply the overlying epidermis by diffusion of nutrients through fenestrated capillaries.

Embryology is a fascinating subject and is the foundation of the development, growth, and maturation of all the cells, organs, and tissues of the body. Strictly, embryology is the study of the early processes of development beginning at fertilization and following the processes that turn a single cell into a multicellular organism. It is all about generation of the building blocks required to make a human body. Developmental anatomy is the study of how these building blocks are turned into specific cells, tissues, and organs as well as the general growth of the body. As you will soon appreciate in the following paragraphs, all organs and systems do not develop at the same rate so there is a degree of overlap between embryology and developmental anatomy. For example, the heart and circulatory system must develop and be functioning very early in development to ensure adequate supplies of nutrients to the developing fetal tissues. Teeth, on the other hand, are not going to be used until about six months after birth at the earliest; while the heart is already beating away, each developing tooth is merely a tiny group of cells bearing little resemblance to a fully formed tooth. Human gestation is considered to take nine months; more accurately, it usually lasts for 38 to 39 weeks from fertilization to birth. Clinically, it is divided into three trimesters of three months each. In this chapter, we will focus on events in the first few weeks. During the first two and a half weeks after fertilization, the very basic building blocks are formed from the single fertilized cell; this is the pre-embryonic period. The embryonic period covers the next five and half weeks during which these basic building blocks develop into the cells, tissues, and organs. As already indicated, some of these may be in a very rudimentary state at the end of the embryonic period. The remaining 30 or so weeks is the fetal period when the tissues and organs of the body grow and develop and the fetus grows considerably. We are not fully mature organisms at birth and have another 20 years a-growing.

Early scientific knowledge recognized two basic types of substances: beneficial ones (such as foods and medicines), and harmful ones (those that cause sickness or death). The latter were designated as poisons. Modern science acknowledges that such a strict division is not justified. As early as the sixteenth century, Paracelsus recognized that ‘‘the right dose differentiates a poison and a remedy.’’ Many chemical substances or mixtures exert a whole spectrum of activities, ranging from beneficial to neutral to lethal. Their effect depends not only on the quantity of the substance to which an organism is exposed, but also on the species and size of the organism, its nutritional status, the method of exposure, and several related factors. Alcohol is a good example. Taken in small quantities, alcohol may be harmless and sometimes even medically recommended. However, an overdose causes intoxication and, in extreme cases, death. Similarly, vitamin A is required for the normal functioning of most higher organisms, yet an overdose of it is highly toxic. If the biological effect of a chemical is related to its dose, there must be a measurable range between concentrations that produce no effect and those that produce the maximum effect. The observation of an effect, whether beneficial or harmful, is complicated by the fact that apparently homogeneous systems are, in fact, heterogeneous. Even an inbred species will exhibit marked differences among individuals in response to chemicals. An effect produced in one individual will not necessarily be repeated in another one. Therefore, any meaningful estimation of the toxic potency of a compound will involve statistical methods of evaluation. To determine the toxicity of a compound for a biological system, an observable and well-defined end effect must be identified. Turbidity or acid production, reflecting the growth or growth inhibition of a culture, may be used as an end point in bacterial systems. In some cases, such as in the study of mutagenesis, colony count may be used. Similarly, measures of viable cells, cell protein, or colony count are useful end points in cell cultures.

Abstract: This chapter recounts bioprinting studies of skin, bone, skeletal muscle, and neuromuscular junctions. The chapter begins with a study of bioprinted skin designed to enable the creation of skin with a uniform pigmentation. The chapter relates two very different approaches to bioprinted bone: a synthetic bone called hyperelastic bone and a strategy that prints cartilage precursors to bone and then induces the conversion of the cartilage to bone by judicious choice of bioinks. Muscles move bone, and the chapter discusses an investigation of bioprinted skeletal muscle. Finally, the chapter considers an attempt to bioprint a neuromuscular junction, a synapse—a minute gap—of about 20 billionths of a meter between a motor neuron and the cell membrane of a skeletal muscle cell. A motor neuron is a nerve in the central nervous system that sends signals to the muscles of the body.

The skin is the boundary between fish and environment and possesses important boundary functions such as protection and camouflage. Fish skin is mucigenic, contrasting with keratinized skin in terrestrial vertebrates. Structurally, there is an outer epidermis, a dermis and an inner hypodermis, the entire mucigenic epidermis remaining alive, with mitotic cells, unlike a keratinized epidermis. A variety of specialized epidermal cells are described, and the role of the ‘bias-sleeve’ orientation of dermal collagen is discussed. Scales, scutes and bony plates have protective roles. The variety of morphological types is considered. Skin colouration has important boundary functions in fish; colour largely depends upon different kinds of chromatophores, mainly dermal, and may change under hormonal or neural control in some species. Seasonal changes may occur in skin structure which can also be affected by captivity. Pollutants such as oil can affect fish skin structure both directly and systemically by influencing hormonal activity.

The skin is an organ that serves many functions in maintaining homeostasis in the body (Bryant, 2000). A wide range of diseases manifest in changes in the skin and its appendages, and because the skin is visible and its disorders are often disfiguring, skin disorders can cause emotional and psychological stress for children and their families (Ball & Bindler, 2007). Skin diseases affect 20–33% of the population at any one time, seriously interfering with activities in 10% (Byrant, 2000). Epidemiological evidence suggests that many cases of skin disease do not reach the general practitioner (GP) or even the local pharmacist; nevertheless, each year about 15% of the population consult their GPs about skin complaints (Bryant, 2000). Skin disorders are among the most common health problems in children (Butcher & White, 2005). The infant and child are possibly more vulnerable to the effects of skin disorders and breakdown due to their underdeveloped integumentary system. Understanding the normal condition of the skin can help in the identification of abnormal signs and prompt treatment of skin disorders (Butcher & White, 2005). This chapter will focus on the integumentary system of the child, with reference to the normal structure of the skin together with common alterations and injuries to the skin of the child and the skills required for their nursing management. At the end of this chapter you should be able to do the following: ● Understand the normal child skin anatomy and physiology. ● Understand the fundamentals of a skin assessment in a child. ● Develop an awareness of the management of common skin alterations. ● Understand the nature and treatment of a child with a skin injury. The skin of an infant or child is normally fundamentally the same as that of an adult, although the blood and nerve supplies are immature and the dermis thinner, with less collagen and fewer elastic fibres. This means that the skin is fragile and can be more easily damaged through physical and mechanical trauma (Turnball, 2007). The skin of a newborn is found to have lanugo, which is a very fine, soft, and unpigmented coat of hairs covering its body until it is shed about 14 days after birth.

Eyelid retraction has numerous causes. Most notably eyelid retraction is caused by thyroid eye disease (TED), trauma, and postsurgical changes. The upper eyelid margin is typically measured at 3.5 to 4.5 mm above the center of the cornea. The lower eyelid margin is typically situated at the inferior border of the limbus. Eyelid retraction is a condition in which the upper eyelid margin is displaced superiorly or the lower eyelid margin is displaced inferiorly. Eyelid retraction may result in exposure keratopathy and disturbing ocular symptoms, including blurred vision, photophobia, foreign body sensation, burning, and reactive tearing. Eyelid retraction in TED is thought to be due to a combination of inflammation, fibrosis, and adrenergic stimulation of the eyelid retractors. Proptosis can also contribute to eyelid retraction. In the upper eyelid, factors responsible for eyelid retraction include (1) inflammation and fibrosis of the levator and Müller’s muscles, (2) adrenergic stimulation of Müller’s muscle, and (3) inflammation and fibrosis of the inferior rectus muscle, causing hypodeviation of the globe and compensatory overaction of the superior rectus–levator complex. In the lower eyelid, factors responsible for eyelid retraction include (1) inflammation and fibrosis of the inferior rectus muscle with consequent traction on its anterior extension, the capsulopalpebral fascia, which is the main lower lid retractor, and (2) adrenergic stimulation of the smooth muscle fibers within the lower lid retractor complex. A combination of eyelid retraction and proptosis in TED may result in ocular exposure with symptoms of ocular irritation, an undesirable cosmetic appearance, corneal erosion and infection, or (rarely) globe luxation. Mild exposure problems can be managed with topical lubricants. Guanethidine, a topical sympatholytic agent, is of limited usefulness in the management of eyelid retraction due to its variable efficacy and frequent ocular side effects, including irritation, hyperemia, photophobia, pain, edema, burning sensation, and punctate keratitis. It may be more tolerable if used in lower concentrations. Exposure problems in the inflammatory phase of the condition present a special challenge as surgical correction of eyelid retraction is best performed in the pos-tinflammatory, stable phase. Several reports have described using Botulinum toxin injections, 2.5 to 15 U, either subconjunctivally or percutaneously, just above the superior border of the tarsus.

The anophthalmic socket is subject to four major deformities: enophthalmos, exposure, eyelid malposition, and socket contraction. Enophthalmos occurs when there is a lack of soft tissue volume, creating a sunken or hollow appearance. Exposure occurs when a previously placed orbital implant erodes through the ocular surface. Eyelid malposition occurs largely as a consequence of wearing of a prosthesis. Socket contraction occurs when there is insufficient ocular surface area and fornix depth to accommodate a mobile prosthesis. Understanding these disfigurements and their treatments is the goal of this chapter. Anopththalmic enophthalmos is an acquired condition that occurs when there is a lack of orbit volume after removal of the eye. In a typical case 6 mL of volume is lost with removal of the eye. An orbital implant will replace 2 to 4 mL of volume, and a prosthesis will replace 1 to 2 mL of volume. This leaves a volume deficit of 1 to 3 mL. This typical volume deficit can be exacerbated by fat and muscle atrophy secondary to surgery or antecedent trauma. In cases of eyes removed secondary to orbital trauma, unrepaired orbital fractures expand the bony orbit, further exacerbating the lack of orbital soft tissue. After removal of the eye the orbital implant and the inadequate volume of orbital soft tissue tend to settle toward the orbital floor, creating more of a volume deficit in the superior orbit. The orbital fat is somewhat liquid and much of the preaponeurotic fat in the upper eyelid flows posterior and inferior, creating the hollow appearance in the superior fornix of the anophthalmic socket. This deformity is referred to as the superior sulcus deformity and is present in some degree in the majority of anophthalmic sockets. 24-1-1 Diagnosis. History-taking should direct the ophthalmologist toward the cause of the patient’s anophthalmos. If the eye was lost to trauma, the possibility of orbital fractures expanding the orbital volume and exacerbating the condition should be considered. If the socket was radiated, the possibility of radiation-induced orbital soft tissue atrophy should be considered.