Introduction The principal function of the urinary system is the maintenance of water, electrolyte and acid–base homeostasis , which requires that any input into the system is balanced by an equivalent output. The kidney provides the mechanism by which excess water and electrolytes are eliminated from the body, while the ureters , bladder and urethra form the storage and outflow tract. A second major function of…

Liver And Biliary System The liver, like the pancreas, develops embryologically as a glandular outgrowth of the primitive foregut . The major functions of the liver may be summarised as follows: Fat metabolism Oxidising triglycerides to produce energy Synthesis of plasma lipoproteins Synthesis of cholesterol and phospholipid Carbohydrate metabolism Converting carbohydrates and proteins into fatty acids and triglyceride Regulation of blood glucose concentration by glycogenesis, glycogenolysis…

Introduction The function of the gastrointestinal (GI) system is to break down food for absorption into the body. This process occurs in five main phases: ingestion , fragmentation , digestion , absorption and elimination of waste products. Digestion is the process by which food is enzymatically broken down into molecules that are small enough to be absorbed into the circulation. As an example, ingested proteins are…

Introduction The digestive process commences in the oral cavity with the ingestion, fragmentation and moistening of food but, in addition to its digestive role, the oral cavity is involved in speech, facial expression, sensory reception and breathing. The major structures of the oral cavity, the lips, teeth, tongue, oral mucosa and the associated salivary glands, participate in all these functions. Mastication or chewing is the process…

Introduction Respiration is a term used to describe two different but interrelated processes: cellular respiration and mechanical respiration . Cellular respiration is the series of intracellular biochemical processes by which the cell produces energy by metabolism of organic molecules (see Ch. 1). This chapter is concerned with mechanical respiration, which involves the following steps: Air is drawn into the body (to the lungs ) from the…

Introduction All living tissues are subject to the constant threat of invasion by disease-producing foreign agents and microorganisms (pathogens), i.e. bacteria, viruses, fungi, protozoa and multicellular parasites such as worms. These organisms may invade the body, multiply and destroy functional tissue, causing illness and potentially death. Three main lines of defense have consequently evolved: Protective surface mechanisms The innate immune system The adaptive immune system Protective…

Introduction The skeletal system is formed from highly specialised types of supporting/connective tissue. The tissues are made up of collagen and acellular matrix, as well as the cells which synthesise them. Bone provides a rigid protective and supporting framework, the rigidity resulting from the deposition of calcium salts within the collagen and matrix. Cartilage occurs in different forms and provides a smooth articular surface at bone…

Introduction The skin is the largest organ in the body, both in weight and surface area. It shows significant regional variation, with the thickest skin being found on the soles of the feet while the thinnest is the delicate skin on the upper and lower eyelids; some of these variations are illustrated and discussed later in this chapter. The skin is the external body surface and…

Introduction The circulatory system mediates continuous movement of all body fluids, its principal functions being the transport of oxygen and nutrients to the tissues as well as transport of carbon dioxide and metabolic waste products from the tissues. The circulatory system is also involved in temperature regulation and the distribution of molecules (e.g. hormones) and cells (e.g. those of the immune system). The circulatory system has…

Introduction The nervous system provides rapid and precise communication between different parts of the body via the action of specialised nerve cells called neurones . These highly specialised cells are interconnected and function to gather and process information and then generate appropriate response signals. The nervous system is divided into two main parts: The central nervous system (CNS) comprising the brain and spinal cord The peripheral…

Introduction Although all cells are capable of some sort of movement, the dominant function of several cell types is to generate force through contraction . In these specialised contractile cells, movement is generated by interaction of the proteins actin and myosin (contractile proteins). Certain forms of contractile cell function as single-cell contractile units: Myoepithelial cells are an important component of certain secretory glands (see Ch. 5…

Introduction The epithelia (singular: epithelium ) are a diverse group of tissues that include both surface epithelia and solid organs . Surface epithelia cover or line all body surfaces, cavities and tubes and form the interface between different biological compartments. For instance, the epidermis of the skin is exposed to the external environment and the epithelial lining of the gastrointestinal tract is exposed to partially digested…

Introduction Supporting/connective tissue is the term applied to tissues which provide general structure, mechanical strength, space filling (sculpting body shape), and physical and metabolic support for more specialised tissues. Connective tissues usually have three structural properties with corresponding construction materials: Tensile strength to resist pulling, stretching and tearing. This is provided by strong fibres of structural proteins from the collagen family. Elasticity to facilitate return to…

Introduction Blood is a suspension of cells in fluid. It is circulated around the body by the heart and, as a result of this circulation, blood serves as the transport vehicle for gases, nutrients, waste products, cells and hormones. The fluid is known as plasma and a typical sample is composed of 90% water, 8% protein, 1% inorganic salts, 0.5% lipids, 0.1% glucose and other minor…

Introduction The development of a single fertilised egg cell to form a complex multicellular organism involves cellular replication, growth and progressive specialisation ( differentiation ) for a variety of functions. The fertilised egg ( zygote ) divides by a process known as mitosis to produce two genetically identical daughter cells, each of which divides to produce two more daughter cells and so on. Some of these…

Introduction to the Cell Histology is the study of normal cells and tissues, mainly using microscopes. This book describes the histology of normal human tissues, although much of the material applies to other mammals and, indeed, non-mammals. Structure and function are interdependent. Histological structure determines and is determined by the functions of different organs and tissues; the study of one has enriched the understanding and study…