The Skeletal System

1. The Skeletal System Health Sciences I Mrs. Rose

2. Bone Fact’s • Makes up the framework of the body • Consists of 206 individual bones in the adult

4. Functions of Skeletal System • Support structure and provide shape • Protection • Allows for movement and anchorage of muscles • Provides mineral storage • Site of hemopoiesis • Blood cell formation in red marrow of long bones

5. STUCTURE OF BONES • Osteocytes • Microscopic cells of bones • Mature bone cell (osteocyte) • Bone is made up of • 35% organic - is a protein called collagen • degree of flexibility • 65% inorganic - mineral salts (calcium) and water • Give bone its hardness and durability

6. Bone Formation • Embryonic skeleton initially consists of collagenous protein fibers secreted by osteoblasts (primitive embryonic cells) • Later, cartilage is deposited between the fibers • At 8 wks, ossification begins • Mineral matter begins to replace cartilage, creating bone

7. Formation • Infant bones are very soft and pliable because of incomplete ossification at birth • For example: soft spot on a baby’s head: fontanel • Ossification due to mineral deposits will continue through childhood making the bone hard and more capable of bearing weight

10. Structure of Long Bone • A typical long bone contains a shaft: diaphysis • Hollow cylinder of hard, compact bone • Makes a long bone strong and hard yet light enough for movement • At each end is an epiphysis

11. Structure long bone cont • In the center of the shaft is the medullary canal. • Filled with yellow bone marrow, mostly made of fat cells • Marrow contains many blood vessels and some cells which form WBCs, called leukocytes • Yellow marrow functions as a fat storage center • Endosteum: • lining of the marrow canal that keeps the cavity intact

12. Structure cont… • Shaft is compact bone • ends of the shaft • are spongy bone (dissolved bone where less strength is needed) • Ends of the long bone contain the red marrow where some RBCs (erythrocytes) and some WBCs are made • Periosteum: tough fibrous tissue (outside covering of bone) which contains blood vessels, lymph vessels, and nerves • Necessary for bone growth, repair, and nutrition

13. Last on Structure • Covering the epiphysis is a thin layer of cartilage: articular cartilage • Acts as a shock absorber between 2 bones that meet to form a joint

15. Growth • A bone increases its circumference by the addition of more bone to the outer surface of the diaphysis by osteoblasts • bone cells that deposit new bone • As girth increases, bone material is being dissolved from the center: medullary canal (gets larger as diameter increases)

16. Growth • Dissolution of bone from the medullary canal results from the action of cells called osteoclasts • Immense bone cells that secrete enzymes • Enzymes digest bony material, splitting the bone minerals (calcium and phosphorus) and enabling them to be absorbed by the surrounding fluid • Medullary canal eventually fills with yellow marrow

17. Growth • Avg growth in females: 18 years • Avg growth in males: 20-21 years

18. Bone Types • Four types: • 1. Long bones: found in upper and lower arms and legs • 2. Flat bones: skull/head bones and ribs • 3. Irregular bones: bones of spinal column • 4. Short bones: wrist and ankle bones

20. PARTS OF THE SKELETON • Axial • Skull, spinal column, ribs, sternum (breast bone), and hyoid (U-shaped bone in the neck – tongue attached to it) • Appendicular • Shoulder girdle, arms, wrists, hands, hip girdle (pelvis), legs, ankles, and feet

23. Axial Skeleton • Skull: cranium and facial bones • 22 bones total • Cranium houses and protects the brain • Facial bones guard and support the eyes, ears, nose, and mouth • Some facial bones are made of bone and cartilage for example the nose (which part is bone and which is cartilage?)

24. Cranium • Cranial bones are thin and slightly curved • During infancy they are held together by an irregular band of connective tissue called a suture • As the child grows, the connective tissue ossifies and turns into hard bone • The dome shape gives better protection than a flat surface, deflecting blows directed toward the head

26. 8 Cranium Bones • 1 frontal: forms the forehead • 2 parietal: form the roof and sides of the skull • 2 temporal: house the ears • 1 occipital: forms the base of the skull and contains the foramen magnum (what is that?) • 1 ethmoid: (located b/t the eyes) forms part of the nasal septum • 1 sphenoid: (resembles a bat) considered the key bone of the skull; all other bones of the skull connect to it

28. 14 Facial Bones • 5 nasal • 2 are bones that form the bridge of the nose • 1 is the vomer bone which forms the lower part, or midline, of the nasal septum • 2 are inferior concha which make up the side walls of the nasal cavity • 2 maxilla: make up the upper jaw • 2 lacrimal: (in the inner aspect of the eyes) contain the tear ducts • 2 zygomatic: form the prominence of the cheek • 2 palatine: form the hard palate of the mouth • 1 mandible: lower jaw and the only movable bone in the face

30. Spinal Column/Vertebra • Strong and flexible, supports the head, provides for attachment of the ribs, and encloses the spinal cord • Consists of small bones: vertebrae • Separated from each other by pads of cartilage tissue called intervertebral disks • Cushions b/t the vertebrae and act as shock absorbers • During our lifetime they become thinner, accounting for loss of height as we age

31. 5 Sections of Vertebral Column • Cervical vertebra • Thoracic vertebra • Lumbar vertebra • Sacrum • Coccyx

33. Cervical Vertebrae • 7 total; located in the neck area • Atlas: the first cervical vertebra that articulates, or is jointed, with the occipital bone; permits us to nod our heads • Axis: the 2nd vertebra; is the odontoid process which forms a pivot on which the atlas rotates; permits us to turn our heads

34. Thoracic and Lumbar Vertebrae • Thoracic: 12 total; located in the chest area • Articulate with the ribs • Lumbar: 5 total; located in the back • Have large bodies that bear most of he body’s weight

36. Sacrum and Coccyx • Sacrum: wedge-shaped bone formed by 5 fused bones • Forms the posterior pelvic girdle and serves as an articulation point for the hips • Coccyx: known as the tailbone • Formed by 4 fused bones

37. Ribs and Sternum figure 6-7 • Thoracic area protected and supported by the thoracic vertebrae, ribs, and sternum • Sternum: (breastbone) is divided into 3 parts: • upper region (manubrium), the body, and a lower cartilaginous part: the xiphoid process • Attached to each side of the upper region , by means of ligaments, are the 2 clavicles(collar bones)

38. continued • Human body contains 12 pairs of ribs • 7 pairs of costal cartilages join 7 pairs of ribs directly to the sternum • True ribs • Next 3 pairs are attached to the 7th rib (instead of the sternum) by their costal cartilages • False ribs • Last 2 pairs are not connected to costal cartilages or sternum • Floating ribs

39. The Appendicular Skeleton Upper Extremities shoulder girdles arms wrist hands Lower Extremities hip girdle legs ankles feet

40. Shoulder Girdle • Also called pectoral girdle • Consists of 4 bones • 2 clavicles (collar bones) • 2 triangular scapulae (shoulder bones) • Clavicles help to brace the shoulders and prevent excessive forward motion • Scapulae permit the attachment of muscles that assist in arm movement and serve as a place of attachment for the arms

41. Arm • Consists of the humerus, radius, and ulna • Humerus • Upper arm – 2nd largest in body • Upper end articulates with the scapulae • Forearm • Radius on thumb side (RADIAL PULSE SITE) • Rotates around the ulna- good flexibility • Ulnaon pinky side • Limited movement • Olecranon process(FUNNY BONE) articulates with the humerus

42. Hand • Has 27 bones • Carpals (wrist bone): consists of 8 small bones arranged in 2 rows • Metacarpals (5) • Phalanges (14) – each finger has 3, the thumb has 2

43. Pelvic Girdle • 3 bones in youth • ilium, ischium, and pubis • Eventually fuse with the sacrum to form a bowl-shaped structure (the pelvic girdle) • Eventually the 2 sets of bones form a joint with the bones in the front: symphysis pubis and with the sacrum in the back: sacroiliac joint

44. Male vs Female Pelvis • Female pelvis is wider • Necessary for childbirth • Male pelvis is heavier

45. Upper Leg • Femur (thigh) • LONGEST and STRONGEST bone in body • Upper part of the femur has a smooth, rounded head • Fits neatly into a cavity of the ilium known as the acetebulum, forming a ball and socket joint

46. Lower Leg • Consists of 2 bones: • Tibia: largest of the 2 • Fibula • The patella (kneecap) is found in front of the knee joint; it is a flat, triangular, sesamoid bone • Formed in the tendons of the quadricep in front of the femur • 4 bursae surround the patella which serve to cushion the knee joint

47. Sesamoid Bone • Found where a tendon passes over a joint • Holds the tendon slightly farther away from the center of the joint and thus increases its movement • Prevents the tendon from flattening into the joint as tension increases

48. Ankle • 7 tarsal bones which provide a connection b/t the foot and leg bones • Largest ankle bone is the heel bone or calcaneus • Tibia and fibula articulate with a broad tarsal bone called the talus • Movement is a sliding motion, allowing the foot to extend and flex when walking

49. Foot • Has 5 metatarsal bones • Arranged to form 2 distinct arches • One runs longitudinally from the calcaneus to the head of the metatarsals: longitudinal arch • Other lies perpendicular to the longitudinal arch: transverse arch • Arches strengthen the foot and provide flexibility and springiness to the stride • Strong ligaments and leg muscle tendons help to hold the foot bones in place

50. Foot continued • Arches can “fall” d/t weak foot ligaments and tendons • Downward pressure by weight of the body slowly flattens them, causing fallen arches or flatfeet • Cause a good deal of stress and strain on the foot muscles • Factors leading to it may be: fatigue, overweight, poor posture, and improperly fitting shoes