Tutorial 1

Skull: Baby and Adult

The skull is the bony section of the head. The skull encases and protects the brain, houses the brain senses, provides attachments for muscles of the head and neck, and helps to form the first portions of the respiratory and digestive tracts. The skull rests on the first vertebra, which is called the "Atlas". At birth, the skull is large in comparison to the rest of the body, and a baby's skull is compressible. The "soft spots" in a baby's head harden and grow together until the bones meet and mesh like a jigsaw puzzle. The largest of the six main soft spots is a diamond-shaped area near the middle of the top of the skull. This is the last area to harden and close, usually at about the age of eighteen months. "Skullduggery" is some kind of trick or some unscrupulous behavior.

Haversian System

Compact bone is very hard and dense. It consists of microscopic cylindrical structures oriented parallel to the long axis of a bone. The cylindrical, column-like structures are the Haversian systems and are laid down in concentric rings called lamellae. Each of these systems is in turn interconnected to other systems to provide a continuous network of blood vessels and nerves.

Carpal Bones

The skeleton of the wrist consists of eight small "carpal bones" that are firmly bound in two rows of four bones each. The resulting mass is the "carpus." The eight bones are the "pisiform," "triangular" or "triquetrum," the "pisiform," "lunate," and "scaphoid" on the upper end of the wrist, where it connects with ligaments and the lower arm bones, and the "hamate," "capitate," "trapezoid," and "trapezium" on the lower side of the hand by the "metacarpals," or first joint of the fingers.

Condyles of The Humerus

At the lower end of the humerus (upper arm bone) and the femur, there are two smooth condyles (rounded processes of the bone): a knob-like "capitulum" on the lateral side and a pulley-shaped "trochlea" in the middle. The capitulum unites with the radius (smaller lower arm bone) at the elbow, and the trochlea is a notch which joins ligaments to the head of the ulna (larger lower arm bone). Above the condyles on either side are "epicondyles," which provide attachments for muscles and ligaments of the elbow. The one toward the center of the arm is the "medial epicondyle," and the one to the side is the "lateral epicondyle."

Capsule of The Shoulder Joint

A "capsule" is a membrane or sac enclosing a body part, usually a joint. "Capsular ligaments" are surrounded and reinforced by muscles tendons, and ligaments, which are largely responsible for keeping the adjoining parts together. The "joint capsule" of the shoulder is attached along the outside ring of the genoid cavity and the anatomical neck of the humerus. Although it completely covers the joint, the capsule is very loose and by itself would be unable to keep the bones of the joint in close contact without the aid of the fibers around it. The joint capsule of the elbow has sides which are thickened by ulnar and radial collateral ligaments. The front surface of the capsule is reinforced by fibers from a muscle (brachialis) in the upper arm.

Phalanges

The phalanges are the small bones that make up the skeleton of the fingers, thumb and toes. Each finger and smaller toe has three phalanges; the thumb and big toe each have two. The phalange nearest the body of the hand or foot is call the "proximal" phalange; the one at the end of each digit is the "distal" phalange; and, of course, when there are three, the middle one is called the "middle" phalange.

A Vertebra

A typical vertebra has a drum-shaped "body" (centrum) that forms a thick, anterior portion of the bone. A longitudinal row of the bodies supports the weight of the head and trunk. The intervertebral disks, which separate joining vertebrae, are fastened to the roughened upper and lower surfaces of the bodies. These disks cushion and soften the forces created by walking and jumping, which might otherwise fracture the vertebrae or jar the brain. Each intervertebral disk is composed of a band of fibrous fibrocartilage (anulus fibrosus) that surrounds a gelatinous core, called the "nucleus pulposus." The bodies of adjacent vertebrae are joined on the front surfaces by "anterior ligaments" and on the back by "posterior ligaments." Projecting from the back of each body are two short stalks called "pedicles." They form the sides of the "vertebral foramen." Two plates (laminae) arise from the pedicles and fuse in the back to become "spinous process." The pedicles, laminae, and spinous process together complete a bony vertebral arch around the vertebral opening, through which the spinal cord passes. Between the pedicles and laminae of a typical vertebra is a "transverse process" that projects laterally and toward the back. Various ligaments and muscles are attached to the spinal process and the transverse process. Projecting upward and downward from each vertebral arch are "superior" and "inferior articulating processes." These processes bear cartilage-covered facets by which each vertebra is joined to the one above and the one below it. On the surfaces of the vertebral pedicles are notches that align to create openings, called "intervertebral foramina." These openings provide passageways for spinal nerves that proceed between joining vertebrae and connect to the spinal cord.

Femur

The "femur" is the thigh bone, the longest bone in the body. The lower end joins the tibia (shin) to form the knee joint. The upper end is rounded into a ball (or "head" of the femur) that fits into a socket in the pelvis to form the hip joint. Just below the head is a constriction, or neck, and two large processes - an upper, lateral "greater trochanter" and a lower, medial "lesser trochanter." These processes provide attachments for muscles of the legs and buttocks. The neck of the femur gives the hip joint a wide range of movement, but it is a point of weakness and a common site of fracture.

Humerus

The humerus is the bone of the upper arm. The smooth, dome-shaped head of the bone lies at an angle to the shaft and fits into a shallow socket of the scapula (shoulder blade) to form the shoulder joint. Below the head, the bone narrows to form a cylindrical shaft. It flattens and widens at the lower end and, at its base, it joins with the bones of the lower arm (the ulna and radius) to make up the elbow. Some people say the "funny bone" is named because it is next to the humerus. It really isn't a bone at all, but is the ulnar nerve, which passes under a prominence of the humerus, where it is vulnerable. To find the funny bone, put the point of the right elbow on a table. Above and to the left of the point is a big knob. When it is struck, the blow pushes the nerve against this knob, causing temporary paralysis. It is no laughing matter, but it is a "funny" feeling.

Fibula

The fibula is the outer and thinner of the two long bones of the lower leg. It is much narrower than the other bone (the shin), to which it runs parallel and to which it is attached at both ends by ligaments. The upper end of the fibula does not reach the knee, but the lower end descends below the shin and forms part of the ankle. Its main function is to provide attachment for muscles. It doesn't give much support or strength to the leg, which explains why the bone can safely be used for grafting onto other bones in the body.