Introduction of Anatomy

 

History 

• From three hundreds BC and second century. 
• Scientist, doctors and artist would experiment and practice on the deaf body. 
• Cadavers were positioned flat on their backs, thus making it easier to draw and reference from that position. 

Definition 

•   It is a Greek word (Ana-Tome) :meaning cutting up. 
• Anatomy - the study of the structure of boby parts and their relationship to one another. 

Subdivisions 

• Gross anatomy 
• Microscopic anatomy 
• Developmental anatomy 
• Specialized branches of anatomy 

Microscopic anatomy

• Cytology - study of the cell 
• Histology - study of tissues

Gross anatomy 

• Regional -all structures in one part of the body (such as the abdomen or leg) 
• Systemic - gross anatomy of the body studied by system
• Surface -study of internal structures as they relate to the overlying skin

Specialized branches of anatomy

• Pathological anatomy -study of structural changes caused by disease 
• Radiographic anatomy-study of internal structures visualized by x ray 
• Molecular biology -study of anatomical structures at a sub -cellular level

Human skeleton 

             Human skeletal system consists of bones and cartilage. The skeletal system consists of bones and cartilage. The skeleton acts as a framework that supports soft tissues. It allows free movement through the action of muscles across joints. The study of bones and cartilage is called osteology. 

Structure of Bone 

              An individual bone is composed of a variety of tissues, including bone tissues, cartilage, fibrous connective tissue, blood and nerve tissue. The terminal broad parts are called epiphysis and the middle part along the length of bone is called diaphysis Or shaft. Which also contains a central cavity filled by yellow bone marrow . The outer connective tissue around the bone is called periosteum and the inner region is call d endosteum. The endosteum further consists of a peripheral part, called compact bone and the inner bone mass, called spongy bone. Most of the spongy bone is present in epiphysis. The red bone marrow is also found in the spaces of spongy bone. 

              These are three types of cells associated with bone (derived from osteogenic cells) i.e., osteoblasts arr bone forming cells that synthesize and secrete unmineralized ground substance. Once the osteoblasts are surrounded by matrix, they become the osteocytes. Osteocytes maintain healthy bone tissue by secreting enzymes and influencing bone mineral content. They also regulate the calcium release from bone tissue to blood. Osteoclasts are bone destroying cells. Osteoclasts perform bone resorption, i.e., they breakdown bone and deposit calcium and phosphate in the blood. The work of osteoclasts is important to the growth and repair of bone. 

Structure of cartilage 

        Cartilage is not strong as bone. It is present at particular places only. It is more flexible than the bone because the matrix is gel like and contains many collagenous and elastic fibres. The cartilage matrix is covered by a dense layer of collagen fibres, called perichondrium. There are may small cavities distributed in the matrix called lacunae which contain cartilage cells. The living cells of cartilage are called chondrocytes. Unlike other connective tissues, cartilage does not contain blood vessels and the chondrocytes are supplied by diffusion. Because of this, it heals very slowly. Although the human skeleton is initially made up of cartilages and fibrous membranes,most of these early supports are soon replaced by bones. A few cartilages that remain in adults are three types. Hyaline cartilage is found at the ends of long bones and in the nose, at larynx and trachea. Fibrocartilage contains wide rows of thick collagenous fibres us found in the disks located between the vertebrae, cartilage of knee. Elastic cartilage is found in the ear flaps and epiglottis. 

Divisions of human skeleton 

          Human skeletal system consists of 206 bones which are primarily divided into two division i.e., axial skeleton and appendicular skeleton. 

Axial skeleton

           Axial skeleton includes those skeletal parts which are present along the central axis of the body, like skull, vertebral column and rib cage. 

Head bones 

         Head contains 29 bones which are divided into four divisions into four divisons i.e.., cranial bones, facial bones, ear ossicles and hyoid bone. Cranial bones form cranium (brain box). Out of 8 cranial bones two are paired i.e., parietal bones (left and right) and temporal bone (left and right) while four are unpaired like frontal bone, occipital bone, ethmoid bone, sphenoid bone. Facial bones are fourteen in number and are attached to the cranium to form face. The six paired bones of face are;lacrimal, zygomatic, nasal bones, inferior nasal concha, maxilla and palatine. The unpaired bones of face are mandible and vomer. Three pairs of middle ear ossicles are malleus, incus and stapes. Hyoid  bone is a small single bone which lies at the base of skull below the tongue. It does not articulate with any other bone of head. 

Vertebral column 

         The vertebral column in human being consists of thirty-three vertebrae. The vertebrae may be divided into following five groups:

(a) cervical vertebrae -7, (b) Thoracic vertebrae -12 (c) Lumbar vertebrae -5 (d) Sacral vertebrae-5 (e) coccygeal vertebrae -4. Cervical vertebrae are the vertebrae of the neck. The atlas is the first cervical vertebra. Axis is the second cervical vertebrae.Thoracic vertebrae are rib carrying vertebrae having large spinous processes and are found in chest region. Lumbar vertebrae are present in abdominal region . Sacral vertebrae are five fused vertebrae forming the sacrum. The sacrum articulates with the illiac bones of the hip bone to form the back of the pelvis. Coccygeal vertebrae or coccyx are four vertebrae fused in the adults. Sacral and coccygeal vertebrae are together called pelvic vertebrae. 

Rib cage 

       The rib cage consists of twelve pairs of ribs. The ribs articulate posteriorly with the thoracic vertebrae. Ten ribs articulate posteriorly with the thoracic vertebrae. Ten ribs are connected anteriorly with sternum with sternum either directly or through the costal cartilage. The rib cage provides support for a semi-vacuum chamber called chest cavity. The seven pairs of ribs that attach directly to the sternum are called true ribs. The 8th , 9th and 10th are called false ribs, as these three pairs of ribs are attached to the sternum by means of common costal cartilage. 11th and 12th pairs of ribs are known as floating ribs, because they do not attach to the sternum. 

Appendicular skeleton 

        Appendicular skeleton includes those skeletal parts which are present in appendages (arms and legs) . These are pectoral girdle, pelvic girdle, forelimbs and hind limbs. 

Pectoral girdle and upper limb 

         Pectoral girdle consists of a pair of clavicles and a pair of scapula. Clavicles are a pair of collar bones. One end of each curved bone articulates with the sternum. The other end articulates with the scapula. Scapulas are two shoulder blades. 

          Upper limb or forelimb consists of humerus, ulna, radius, carpals, metacarpals and phalanges. Humerua is a long bone, the end of which has a spherical head. Which fits into the glenoid cavity. Radius is a long, outer bone of the forearm (on the thumb side). Ulna is a long bone on the inner side of the forearm, and slightly bigger tha  radius. Caroals consists of two rowa of eight short bones forming the wrist. The upper row articulates with the radius and forms the wrist joint. Metacarpals consist of five bones making up the palm of the hand. Each finger possesses three phalanges except thumb which comprises two phalanges. 

Pelvic girdle and lower limb 

         The pelvic girdle is made up of three units the ileum, ischium and pubis which form coxa. The two halves of the pelvic girdle are joined at the pubic symphysis. A cavity called acetabulum us also present. 

       Lower limb or hind limb consists of femur, patella, tibia, fibula, tarsal, metatarsal and phalanges. Femur or the thighbone is a long bone with head, which fits into the acetabulum. Patella or the kneecap is embedded in a long tendon which runs over the knee joint. Tibia or shin bone is the large bone in the leg. Fibula or outer bone is a thin bone joints the tibia just below the knee joint and just above the ankle. Tarsal is made of seven bones which are tightly attached to form the ankle. Metatarsal consists of five bones which articulate with the tarsal  and phalanges to form the sole of the foot. Phalanges are small bones which make up the toes. Each toe of the foot possesses three phalanges except bif toe, which comprises of two phalanges 

Joints 

    A joint or articulation is a place where two bones and  bone and cartilage cone together. The scientific study of the structure and function of joints is called arthrology. The joints are classified as fibrous joints (immoveable) . Cartilaginous joints (slightly moveable) and synovial joints (freely moveable). 

Fibrous joints 

      When the adjacent bones are directly connected to each other by fibrous connective tissue consisting mainly of collagen, it is called fibrous joint. In this joint the bones do not have a joint cavity between them. The gap between the bones may be narrow or wide. 

• Most bones of the skull called suture. 
• The shaft regions of the long bones in the forearm and in the leg. 
• The root of a  tooth and the socket in the maxilla or mandible(jawbones) 

Cartilaginous joints 

        At a cartilaginous joint, the adjacent bones are united by cartilage, a tough but flexible type of connective tissue. These types of joints lack a joint cavity and involve bones that are joined together by either hyaline cartilage or fibrocartilage. Cartilaginous joints allow little movement. The examples of cartilaginous joint are:

• Costal cartilages that attach ribs to the sternum
• Pubic symphysis and intervertebral disc. 

Synovial joints

       They are freely moveable joints. The ends of bones are covered with hyaline cartilage and held together by a surrounding,tube like capsule is composed of an outer layer of ligaments and an inner lining if synovial membrane, which secretes synovial fluid. 

Examples: hinge joints, pivot joint, ball and socket joint, gliding joint. 

    

                Dr. Mahalakshmi Raghunath

                Reference

               Author: Dr. N. Senthil kumar