SUPPORT

MOVEMENT

PROTECTION

MINERAL RESERVOIR 99% Ca; 90% P – 2/3 weight of bone

HEMOPOIESIS

 

LONG BONES

SHORT BONES

FLAT BONES

IRREGULAR BONES

 

GROSS ANATOMY

DIAPHYSIS

EPIPHYSIS

EPIPHYSEAL CARTILAGEOR PLATE

PERIOSTEUM

 

OSTEOGENIC CELLS respond to traumas, such as fractures, by giving rise to bone-forming cells and bone-destroying cells.

OSTEOBLASTS (BONE-FORMING CELLS) synthesize and secrete unmineralized ground substance and are found in areas of high metabolism within the bone.

OSTEOCYTES are mature bone cells made from osteoblasts that have made bone tissue around themselves. These cells maintain healthy bone tissue by secreting enzymes and controlling the bone mineral content; they also control the calcium release from the bone tissue to the blood.

OSTEOCLASTS are large cells that break down bone tissue. They are very important to bone growth, healing, and remodeling.

BONE-LINING CELLS are thought to regulate the movement of calcium and phosphate into and out of the bone.

 

 

 

 

Types of bones

COMPACT BONE

SPONGY BONE

 

COMPOSITION

ORGANIC FRAMEWORK

INORGANIC SALTS

 

EARLY DEVELOPMENT OF BONE

INTRAMEMBRANOUS OSSIFICATION

ENDOCHONDAL OSSIFICATION

INCREASE IN BONE LENGTH AND DIAMETER

CARTILAGE CELLS UNDERGO MITOSIS

DIAPHYSIS SIDE OFEPIPHYSEAL PLATE

INCREASE IN DIAMETER

 

FACTORS THAT AFFECT BONE DEVELOPMENT

STRESS

HORMONES

NUTRITION

 

 

Individual bones of the skeleton

 

The human skeleton is divided into two distinct parts:

The axial skeleton consists of bones that form the axis of the body and support and protect the organs of the head, neck, and trunk.

The Skull

The Sternum

The Ribs

The Vertebral Column

The appendicular skeleton is composed of bones that anchor the appendages to the axial skeleton.

The Upper Extremities

The Lower Extremities

The Shoulder Girdle

The Pelvic Girdle

SKULL is the bony framework of the head. It is comprised of the eight cranial and fourteen facial bones.

CRANIAL BONES

The cranial bones makeup the protective frame of bone around the brain. The cranial bones are:

·FRONTAL forms part of the cranial cavity as well as the forehead, the brow ridges and the nasal cavity.

·left and right PARIETAL forms much of the superior and lateral portions of the cranium.

·left and right TEMPORAL form the lateral walls of the cranium as well as housing the external ear.

·OCCIPITAL forms the posterior and inferior portions of the cranium. Many neck muscles attach here as this is the point of articulation with the neck.

·SPHENOID forms part of the eye orbit and helps to form the floor of the cranium.

·ETHMOID forms the medial portions of the orbits and the roof of the nasal cavity.

FACIAL BONES

The facial bones makeup the upper and lower jaw and other facial structures. The facial bones are:

·MANDIBLE is the lower jawbone. It articulates with the temporal bones at the temporomandibular joints. This forms the only freely moveable joint in the head. It provides the chewing motion.

·left and right MAXILLA are the upper jaw bones. They form part of the nose, orbits, and roof of the mouth.

·left and right PALATINE form a portion of the nasal cavity and the posterior portion of the roof of the mouth.

·left and right ZYGOMATIC are the cheek bones. They form portions of the orbits as well.

·left and right NASAL form the superior portion of the bridge of the nose.

·left and right LACRIMAL help to form the orbits.

·VOMER forms part of the nasal septum (the divider between the nostrils).

·left and right INFERIOR NASAL CONCHA (=turbinate) forms the lateral walls of the nose and increase the surface area of the nasal cavity.

STERNUM is a flat, dagger shaped bone located in the middle of the chest. Along with the ribs, the sternum forms the rib cage that protects the heart, lungs, and major blood vessels from damage.

The sternum is composed of three parts:

MANUBRIUM also called the "handle", is located at the top of the sternum and moves slightly. It is connected to the first two ribs.

BODY, also called the "blade" or the "gladiolus", is located in the middle of the sternum and connects the third to seventh ribs directly and the eighth through tenth ribs indirectly.

XIPHOID PROCESS, also called the "tip", is located on the bottom of the sternum. It is often cartilaginous (cartilage), but does become bony in later years.

These three segments of bone are usually fused in adults.

The sternum serves an important function in the body. The ribs are connected to it by the costal cartilage. Without the sternum, there would be a hole in the bone structure in the middle of your chest, right above your heart and lungs. The sternum protects this vital area and completes the circle of the rib cage.

The ribs are thin, flat, curved bones that form a protective cage around the organs in the upper body. They are comprised 24 bones arranged in 12 pairs.

These bones are divided into three categories:

The first seven bones are called the vertebrosternal ribs (true ribs). These bones are connected to the spine (the backbone) in back. In the front, the true ribs are connected directly to the breastbone or sternum by a strips of cartilage called the costal cartilage.

The next three pairs of bones are called vertebrochondral ribs (false ribs). These bones are slightly shorter than the true ribs and are connected to the spine in back. However, instead of being attached directly to the sternum in front, the false ribs are attached to the lowest true rib.

The last two sets of rib bones are called vertebral ribs (floating ribs). Floating ribs are smaller than both the true ribs and the false ribs. They are attached to the spine at the back, but are not connected to anything in the front.

The ribs form a kind of cage the encloses the upper body. They give the chest its familiar shape.

The ribs serve several important purposes. They protect the heart and lungs from injuries and shocks that might damage them. Ribs also protect parts of the stomach, spleen, and kidneys. The ribs help you to breathe. As you inhale, the muscles in between the ribs lift the rib cage up, allowing the lungs to expand. When you exhale, the rib cage moves down again, squeezing the air out of your lungs.

The vertebral column (also called the backbone, spine, or spinal column) consists of a series of 33 irregularly shaped bones, called vertebrae. These 33 bones are divided into five categories depending on where they are located in the backbone.

The first seven vertebrae are called the cervical vertebrae. Located at the top of the spinal column, these bones form a flexible framework for the neck and support the head. The first cervical vertebrae is called the atlas and the second is called the axis. The atlas' shape allows the head to nod "yes" and the axis' shape allows the head to shake "no".

The next twelve vertebrae are called the thoracic vertebrae. These bones move with the ribs to form the rear anchor of the rib cage <../ribs/ribs.html>. Thoracic vertebrae are larger than cervical vertebrae and increase in size from top to bottom.

After the thoracic vertebrae, come the lumbar vertebrae. These five bones are the largest vertebrae in the spinal column. These vertebrae support most of the body's weight and are attached to many of the back muscles.

The sacrum is a triangular bone located just below the lumbar vertebrae. It consists of four or five sacral vertebrae in a child, which become fused into a single bone after age 26. The sacrum forms the back wall of the pelvic girdle and moves with it.

The bottom of the spinal column is called the coccyx or tailbone. It consists of 3-5 bones that are fused together in an adult. Many muscles connect to the coccyx.

These bones compose the vertebral column, resulting in a total of 26 movable parts in an adult. In between the vertebrae are intervertebral discs made of fibrous cartilage that act as shock absorbers and allow the back to move. As a person ages, these discs compress and shrink, resulting in a distinct loss of height (generally between 0.5 and 2.0cm) between the ages of 50 and 55.

When looked at from the side, the spine forms four curve. These curves are called the cervical, thoracic, lumbar, and pelvic curves. The cervical curve is located at the top of the spine and is composed of cervical vertebrae. Next come the thoracic and lumbar curves composed of thoracic and lumbar vertebrae respectively. The final curve called the pelvic or sacral curve is formed by the sacrum and coccyx. These curves allow human beings to stand upright and help to maintain the balance of the upper body. The cervical and lumbar curves are not present in an infant. The cervical curves forms around the age of 3 months when an infant begins to hold its head up and the lumbar curve develops when a child begins to walk.

In addition to allowing humans to stand upright and maintain their balance, the vertebral column serves several other important functions. It helps to support the head and arms, while permitting freedom of movement. It also provides attachment for many muscles, the ribs, and some of the organs and protects the spinal cord, which controls most bodily functions.

 

The upper extremity consists of three parts: the arm, the forearm, and the hand.

The arm, or brachium, is technically only the region between the shoulder and elbow. It consists of a single long bone called the humerus. The humerus is the longest bone in the upper extremity. The top, or head, is large, smooth, and rounded and fits into the scapula in the shoulder. On the bottom of the humerus, are two depressions where the humerus connects to the ulna and radius of the forearm. The radius is connected on the side away from the body (lateral side) and the ulna is connected on the side towards the body (medial side) when standing in the anatomical position. Together, the humerus and the ulna make up the elbow. The bottom of the humerus protects the ulnar nerve and is commonly known as the "funny bone" because striking the elbow on a hard surface stimulates the ulnar nerve and produces a tingling sensation.

The forearm is the region between the elbow and the wrist. It is formed by the radius on the lateral side and the ulna on the medial side when the forearm is viewed in the anatomical position. The ulna is longer than the radius and connected more firmly to the humerus. The radius, however, contributes more to the movement of the wrist and hand than the ulna. When the hand is turned over so that the palm is facing downwards, the radius crosses over the ulna. The top of each bone connects to the humerus of the arm and the bottom of each connects to the bones of the hand.

The hand consists of three parts (the wrist, palm, and five fingers) and 27 bones.

The wrist, or carpus, consists of 8 small bones called the carpal bones that are tightly bound by ligaments. These bone are arranged in two rows of four bones each. The top row (the row closest to the forearm) from the lateral (thumb) side to the medial side contains the scaphoid, lunate, triquetral, and pisiform bones. The second row from lateral to medial contains the trapezium, trapezoid, capitate, and hamate. The scaphoid and lunate connect to the bottom of the radius.

The palm or metacarpus consists of five metacarpal bones, one aligned with each of the fingers. The metacarpal bones are not named but are numbered I to V starting with the thumb. The bases of the metacarpal bones are connected to the wrist bones and the heads are connected to the bones of the fingers. The heads of the metacarpals form the knuckles of a clenched fist.

The fingers are made up of 14 bones called phalanges. A single finger bone is called a phalanx. The phalanges are arranged in three rows. The first row (the closest to the metacarpals) is called the proximal row, the second row is the middle row, and the farthest row is called the distal row. Each finger has a proximal phalanx, a middle phalanx, and a distal phalanx, except the thumb (also called the pollex) which does not have a middle phalanx. The digits are also numbered I to V starting from the thumb.

The lower extremity is composed of the bones of the thigh, leg, foot, and the patella (commonly known as the kneecap).

The thigh is the region between the hip and the knee and is composed of a single bone called the femur or thighbone. The femur is the longest, largest, and strongest bone in the body.

The leg is technically only the region from the knee to the ankle. It is formed by the fibula on side away from the body (lateral side) and the tibia, also called the shin bone, on the side nearest the body (medial side). The tibia connects to the femur to form the knee joint and with the talus, a foot bone, to allow the ankle to flex and extend. The tibia is larger than the fibula because it bears most of the weight, while the fibula serves as an area for muscle attachment.

The foot, or pes, contains the 26 bones of the ankle, instep, and the five toes. The ankle, or tarsus, is composed of the 7 tarsal bones which correspond to the carpals in the wrist. The largest tarsal bone is called the calcaneus or heel bone. The talus rests on top of the calcaneus and is connected to the tibia. Directly in front of the talus is the navicular bone. The remaining bones from medial to lateral are the medial, intermediate, the lateral cuneiform bones, and the cuboid bone.

The metatarsal and phalanges bones of the foot are similar in number and position to the metacarpal and phalanges bones of the hand. The five metatarsal bones are numbered I to V starting on the medial side with the big toe. The first metatarsal bone is larger than the others because it plays a major role in supporting the body's weight. The 14 phalanges of the foot, as with the hand, are arranged in a proximal row, a middle row, and a distal row, with the big toe, or hallux, having only a proximal and distal phalanx.

The foot's two arches are formed by the structure and arrangement of the bones and are maintained by tendons and ligaments. The arches give when weight is placed on the foot and spring back when the weight is lifted off of the foot. The arches may fall due to a weakening of the ligaments and tendons in the foot.

The patella or kneecap is a large, triangular sesamoid bone between the femur and the tibia. It is formed in response to the strain in the tendon that forms the knee. The patella protects the knee joint and strengthens the tendon that forms the knee.

The bones of the lower extremities are the heaviest, largest, and strongest bones in the body because they must bear the entire weight of the body when a person is standing in the upright position.

The Shoulder Girdle, also called the Pectoral Girdle, is composed of four bones: two clavicles and two scapulae .

The clavicle, commonly called the collarbone, is a slender S-shaped bone that connects the upper arm to the trunk of the body and holds the shoulder joint away from the body to allow for greater freedom of movement. One end of the clavicle is connected to the sternum and one end is connected to the scapula.

The scapula is a large, triangular, flat bone on the back side of the rib cage commonly called the shoulder blade. It overlays the second through seventh rib and serves as an attachment for several muscles. It has a shallow depression called the glenoid cavity that the head of the humerus (upper arm bone) fits into.

Usually, a "girdle" refers to something that encircles or is a complete ring. However, the shoulder girdle is an incomplete ring. In the front, the clavicles are separated by the sternum. In the back, there is a gap between the two scapulae.

The primary function of the pectoral girdle is to provide an attachment point for the numerous muscles that allow the shoulder and elbow joints to move. It also provides the connection between the upper extremities (the arms) and the axial skeleton.

The Pelvic Girdle, also called the hip girdle, is composed to two coxal (hip) bones. The coxal bones are also called the ossa coxae or innominate bones. During childhood, each coxal bone consists of three separate parts: the ilium (denoted in purple above), the ischium (denoted in red above), and the pubis (denoted in blue above). In an adult, these three bones are firmly fused into a single bone. In the picture above, the coxal bone on the left side has been divided into its component pieces while the right side has been preserved.

In the back, these two bones meet on either side of the sacrum. In the front, they are connected by a muscle called the pubic symphysis (denoted in green above).

The pelvic girdle serves several important functions in the body. It supports the weight of the body from the vertebral column. It also protects and supports the lower organs, including the urinary bladder, the reproductive organs, and the developing fetus in a pregnant woman.

The pelvic girdle differs between men and woman. In a man, the pelvis is more massive and the iliac crests are closer together. In a woman, the pelvis is more delicate and the iliac crests are farther apart. These differences reflect the woman's role in pregnancy and delivery of children. When a child is born, it must pass through its mother's pelvis. If the opening is too small, a cesarean section may be necessary.

 

Articulations of the body