Chapter 2 Case 2.1 A child with muscle weakness A 2-month-old child is admitted to hospital because his parents are concerned that he has been experiencing difficulty with feeding and becoming breathless. Examination reveals proximal muscle weakness. There is no clinical evidence that the peripheral nerves are involved. Routine blood investigations are normal. In particular, serum creatine kinase levels are normal (the enzyme is released from…

Introduction A vital function of the nervous system is the gathering of sensory information. Sensory information is derived from a variety of specialized sensory nerve endings. These include: Sensory endings in the skin to detect touch (fine touch, pressure), pain and temperature (see Chapter 18 ) Tendon endings and muscle spindles to detect movement and position of the limbs Chemoreceptive organs, such as the carotid body…

Introduction The skin is an extensive organ covering the exterior of the body. It varies in structure from site to site according to specific functions, which include: Protection from external damaging agents (infective, mechanical, thermal) Prevention of loss of water Thermoregulation Sensation (touch, heat, pressure, pain) Secretion of sebum, composed of protective lipids Vitamin D production The breast is a highly modified area of skin with…

Introduction The female reproductive system: Produces haploid female gametes (ova) Receives haploid male gametes (spermatozoa) before fertilization Provides a suitable environment for fertilization of ova by spermatozoa Provides a suitable physical and hormonal environment for implantation of the embryo Accommodates and nourishes the embryo and fetus during pregnancy Expels the mature fetus at the end of pregnancy The structure of the human female reproductive system changes…

Introduction The male reproductive system is responsible for: Production, nourishment and temporary storage of the haploid male gametes (spermatozoa) Intromission of a suspension of spermatozoa (semen) into the female genital system Production of male sex hormones (androgens) Whereas the first two functions are important only during the years of sexual maturity, hormone production is required throughout life, even in utero. The male genital system ( Fig.…

Introduction The main function of the urinary system is the production, storage and voiding of urine. Urine production and the control of its composition are the responsibility of the kidneys. The pelvicalyceal systems and ureters transfer urine from the kidneys to the bladder, and the urethra is the channel through which stored urine is voided from the bladder. The pelvicalyceal systems, ureters, bladder and urethra have…

Introduction Cell communication is vital for any multicellular organism to function efficiently. At a local level, cells communicate via cell surface molecules and gap junctions, whereas remote communication is mediated by the secretion of chemical messengers, which activate cells by interacting with specific receptors. Such secretion may be one of four main types: autocrine, paracrine, endocrine or synaptic ( Fig. 14.1 ). Autocrine secretion occurs when…

Introduction The musculoskeletal system, which provides mechanical support and permits movement, is composed of skeletal muscle, tendons, bones, joints and ligaments. Skeletal muscles act as contractile levers and are connected to bone by tendons. Bones act as rigid levers, articulating with other bones through joints, which are kept in relationship by ligaments. A special characteristic of muscle, tendons and joints is the possession of a rich…

Introduction The liver acts as a vast biosynthetic chemical factory, synthesizing large complex molecules from substances brought to it in the blood, particularly substances recently absorbed by the intestine and transported by a portal blood system. The liver has a wide range of functions, which accounts for its complex structure. All of the biochemical functions of the liver are carried out by the epithelial parenchymal cells…

Introduction The alimentary tract is best considered as a muscular tube lined internally by an epithelium that varies in structure according to specialized functions required at particular sites along its length; with a few local variations, the structure of the musculature is similar throughout. The function of the alimentary tract is to take in raw food material and to fragment it into small portions. These are…

Introduction The respiratory system transfers oxygen from the air into the blood and carbon dioxide from the blood into the air. Blood oxygen is used for cellular respiratory processes that generate carbon dioxide as a by-product. The gaseous exchange occurs in the distal part of the respiratory tract, where air-containing cavities (alveolar sacs) are in intimate contact with thin-walled blood vessels. The proximal part of the…

Introduction The main transport systems are the circulatory systems, in which substances are dissolved or suspended in liquid and carried from one part of the body to another in a series of tubes (vessels). There are two main circulatory systems: the blood circulatory system and the lymphatic system. The blood circulatory system is the main method of transporting oxygen, carbon dioxide, nutrients and metabolic breakdown products,…

Introduction The immune system is part of an array of defence systems used to combat disease. The body must constantly protect itself from invasion by a variety of pathogens, which may gain entry via the skin, gut, respiratory tract and other routes. This protection is provided by a range of cells which together form the immune system. The main cell types involved are white blood cells,…

Introduction The blood is a mixture of cellular elements, fluid, proteins and metabolites. Blood has four major elements: Red blood cells (erythrocytes) transport oxygen from the lungs to the peripheral tissues. White blood cells (leukocytes) have a defensive role, destroying infecting organisms, such as bacteria and viruses, and assisting in the removal of dead or damaged tissues. Platelets (thrombocytes) are the first line of defence against…

Introduction The nervous system allows rapid and specific communication between widely spaced areas of the body by the action of specialized nerve cells (neurons), which gather and process information and 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 nervous system (PNS), comprising the nerves which run between the…

Introduction Several cell types are specialized to generate motile forces through contraction. This chapter presents an overview of the main types of contractile cells. The general structure of each type of cell is described, together with details of their fine structure and how this relates to the molecular basis of contraction. There are four main groups of contractile cells. Contractile cells are specially adapted to generate…

Introduction The cells that form tissues can be divided into two types: parenchymal cells , which provide the main function of a tissue, and support cells , which provide the structural scaffolding of a tissue. Support cells comprise a set of highly developed cell types with complex metabolic functions and produce an extracellular matrix, which largely defines the physical characteristics of a tissue. Support cells and…

Introduction Epithelial cells are sheets of specialized cells that cover and line the interior and exterior surfaces of the body, for example, the outer layers of the skin and the inner luminal surface of the gastrointestinal tract. They have diverse functions such as secretion, absorption and protection (as a barrier), made possible by many specialized surface and internal modifications, with cells attached to each other by…

Introduction Cells of all types have several common defining attributes and are composed of a fluid material ( cytosol ) that contains smaller elements, termed subcellular structures, which provide the framework for cellular activities. Each cell is contained within a cell wall composed of a specialized cell membrane. The fluid inside the cell, the cytosol, is a dense proteinaceous liquid that contains many of the essential…

Introduction Histology is the study of the microscopic structure of biological material and the ways in which individual components are structurally and functionally related. Histology is central to biological and medical sciences, standing at the crossroads between a range of disciplines. Anatomy: sometimes referred to as microscopic anatomy or microanatomy, histology places gross anatomy into context, enabling the understanding of cell and tissue microstructure and how…