Title basic concepts of human anatomy.pdf ✅

Objectives In this chapter you will learn to: • Describe the anatomical position. • Describe the anatomical planes. • Define the anatomical terms used in anatomy and clinical practice. • Describe the terms of movement, including those of the thumb. • Understand the structure of bone. • List the factors that contribute to joint stability. • Describe the classification of muscles according to their actions. • Describe the organization and function of muscle. • Draw a diagram of the components of a spinal nerve. • Describe the layers of a blood vessel wall. • Describe factors causing lymphatic fluid movement and functions of lymph. • Outline the layout of the gastrointestinal system and general functions. • Outline the layout of the urinary system and general functions. Basic concepts of anatomy 1 3 Such anatomical planes are frequently used in computer tomography (CT) scans and magnetic resonance imaging (MRI), to visualize muscle, bone, lung and other soft tissues as well as pathologies, for example pancreatic cancer or a brain abscess. Terms of position The terms of position commonly used in clinical practice and anatomy are illustrated in Figure 1.3. Terms of movement Various terms are used to describe movements of the body (Fig. 1.4): • Flexion—forward movement in a sagittal plane which in general reduces the angle at the joint, e.g. bending the elbow. Exceptions are at the ankle joint (when the angle is increased) and the shoulder joint (when the angle between the upper limb and trunk is increased). • Extension—backward movement in a sagittal plane which in general increases the angle at joints except at the ankle joint (when the angle is decreased) and the knee joint due to lower limb rotation during embryonic development. DESCRIPTIVE ANATOMICAL TERMS The anatomical position This is a standard position used in anatomy and clinical medicine to allow accurate and consistent description of one body part in relation to another (Fig. 1.1): • The head is directed forwards with eyes looking into the distance. • The body is upright, legs together, and directed forwards. • The palms are turned forward, with the thumbs laterally. Anatomical planes These comprise the following (Fig. 1.2): • The median sagittal plane is the vertical plane passing through the midline of the body from the front to the back. Any plane parallel to this is termed paramedian or sagittal. • Coronal (or frontal) planes are vertical planes perpendicular to the sagittal planes. • Horizontal or transverse planes lie at right angles to both the sagittal and coronal planes. Ch01-M3417.qxd 3/19/07 3:22 PM Page 3
Basic Concepts of Anatomy • Abduction—movement away from the median plane. • Adduction—movement towards the median plane. • Supination—lateral rotation of the forearm, causing the palm to face anteriorly. • Pronation—medial rotation of the forearm, causing the palm to face posteriorly. • Eversion—turning the sole of the foot outwards. • Inversion—turning the sole of the foot inwards. • Rotation—movement of part of the body around its long axis. • Circumduction—a combination of flexion, extension, abduction, and adduction. The terms used to describe movements of the thumb are perpendicular to the movements of the body, e.g. flexion of the thumb is at 90° to that of flexion of the fingers (Fig. 1.5). BASIC STRUCTURES OF ANATOMY Skin The skin completely covers the body surface and is the largest organ of the body. The functions of the skin include: • Protection from ultraviolet light and mechanical, chemical, and thermal insults. • Sensations including pain, temperature, touch and pressure. • Thermoregulation. • Metabolic functions, e.g. vitamin D synthesis. The skin is composed of the following (Fig. 1.6): • The epidermis forms a protective waterproof barrier. It consists of keratinized stratified squamous epithelium, which is continuously being shed and replaced. It is avascular. • The dermis supports the epidermis and it has a rich network of vessels and nerves. It is composed mainly of collagen fibres with elastic fibres giving the skin its elasticity. • The hypodermis or superficial fascia. It consists of fatty tissue which provides thermal insulation and protection for underlying structures. 4 neck Posterior view head scapular region back loin buttock Anterior view face arm upper limb forearm hand thigh lower limb leg foot elbow wrist flank groin heel knee hip ankle abdomen shoulder breast thorax Fig. 1.1 Anatomical position and regions of the body. To differentiate supination from pronation remember that you hold a bowl of soup with a supinated forearm. Ch01-M3417.qxd 3/19/07 3:22 PM Page 4
The skin appendages include: • Hairs—highly modified, keratinized structures. • Sweat glands—produce sweat, which plays a role in thermoregulation. • Sebaceous glands—produce sebum, which lubricates the skin and hair. 5 Basic Structures of Anatomy 1 median plane coronal plane inferior superior horizontal plane posterior (dorsal) medial lateral anterior (ventral) Fig. 1.2 Anatomical planes. median plane posterior anterior Superior Inferior medial proximal distal distal proximal lateral Superior Inferior A Dermatology A genetic mutation in collagen synthesis affects the protein’s function. Dermal collagen is normally resistant to stretch, preventing excessive elasticity. However, this is lost in Ehlers–Danlos syndrome where individuals have very elastic skin as well as other features due to collagen in joints (are hyperextendable) or heart valves (mitral valve regurgitation). Fig. 1.3 Relationship and comparison (A) and classification (B) of terms of position commonly used in anatomy and clinical practice. Position Description Anterior In front of another structure Posterior Behind another structure Superior Above another structure Inferior Below another structure Deep Further away from body surface Superficial Closer to body surface Medial Closer to median plane Lateral Further away from median plane Proximal Closer to the trunk or origin Distal Further away from the trunk or origin Ipsilateral The same side of the body Contralateral The opposite side of the body Ch01-M3417.qxd 3/19/07 3:23 PM Page 5
Basic Concepts of Anatomy • Nails—highly specialized appendages found on the dorsal surface of each digit. Fascia The fascia of the body may be divided into superficial and deep layers. The superficial fascia (subcutaneous fatty tissue) consists of loose areolar tissue that unites the dermis to the deep fascia. It contains cutaneous nerves, blood vessels and lymphatics that supply to the dermis. Its thickness varies at different sites within the body and women have a thicker layer than men. In some places sheets of muscle lie in the fascia, e.g. muscles of facial expression. The deep fascia forms a layer of fibrous tissue around the limbs and body and the deep structures. Intermuscular septa extend from the deep fascia, attach to bone, and divide limb musculature into compartments. The fascia has a rich nerve supply and it is, therefore, very sensitive. The thickness of the fascia varies widely: e.g. it is thickened in the iliotibial tract but very thin over the rectus abdominis muscle and absent over the face. The arrangement of the fascia determines the pattern of spread of infection as well as blood due to haemorrhaging into tissues. Bone Bone is a specialized form of connective tissue with a mineralized extracellular component. The functions of bone include: • Locomotion (by serving as a rigid lever). • Support (giving soft tissue permanent shape). • Attachment of muscles. • Calcium homeostasis and storage of other inorganic ions. • Production of blood cells (haematopoiesis). 6 extension extension flexion flexion A B abduction adduction medial rotation lateral rotation plantarflexion = flexion dorsiflexion = extension circumduction supination pronation abduction adduction medial rotation lateral rotation eversion inversion G E F D C Fig. 1.4 Terms of movement. (A) Flexion and extension of forearm at elbow joint. (B) Flexion and extension of leg at knee joint. (C) Dorsiflexion and plantarflexion of foot at ankle joint. (D) Abduction and adduction of right limbs and rotation of left limbs at shoulder and hip joints, respectively. (E) Pronation and supination of forearm at radioulnar joints. (F) Circumduction (circular movement) of lower limb at hip joint. (G) Inversion and eversion of foot at subtalar and transverse tarsal joints. Ch01-M3417.qxd 3/19/07 3:23 PM Page 6