The skeletal system anatomy
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The human skeleton can be divided into two parts: the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones including the skull, vertebral column, ribs, and sternum, and forms the core of the body providing support and protecting organs. The appendicular skeleton is made up of 126 bones organized into the upper and lower limbs, including shoulders, pelvis, arms, forearms, hands, thighs, legs, feet, and ankles. Together the skeleton provides structure, movement, protection, storage, and production of blood cells to the body.
The skeletal system anatomy
- 2. The bones primarily give support to the appendages and protect the fragile organs of the body such as the brain, spinal cord, heart, and lungs. They also store calcium and phoshorus in the hard bone matrix, which can be released when needed elsewhere. The bumps, ridges, and grooves on the surface of bones provide attachment sites for the skeletal muscles. Additionally, many bones contain a soft tissue called marrow that produces new blood cells and stores fat
- 3. Bone is one of the hardest parts of the body Very lightweight Can resist tension ◦ Calcium salts make it hard ◦ Collagen fibers make it strong and flexible
- 4. Support Internal framework of body Ex: Legs support body trunk, rib cage supports chest wall Protection Protects soft body organs (skull protects brain, ribs protect heart and lungs, etc) Movement* Muscles use bones as levers to move body NOT a function skeletal system can do on it’s own Storage Fat storage In yellow marrow Mineral storage Calcium, phosphorus, and others. Blood cell formation Hematopoeisis Occurs in bone marrow of long bones
- 5. The adult human skeleton is a framework of 206 bones and is anatomically divided into two parts, ◦ The axial skeleton ◦ The appendicular skeleton Two types of bone ◦ Compact bone Homogeneous appearance Dense, looks smooth ◦ Spongy bone Small needle-like pieces Lots of open spaces (Looks like a sponge, hence the name)
- 6. In embryos… ◦ Skeleton made of hyaline cartilage ◦ Gets replaced by bone with age Cartilage remains in a few places… ◦ Bridge of nose ◦ Parts of ribs ◦ Joints
- 7. Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Bone replaces cartilage Bones remodeled, lengthened until growth stops Bones change shape somewhat Bones grow in width
- 10. Osteocyte ◦ Mature bone cell Osteoblast ◦ “Bone builders” Osteoclast ◦ “Bone destroyers” ◦ Break down bone matrix to remodel and/or release calcium
- 11. Bone remodeling is done by osteoblasts and osteoclasts Essential for bones to keep normal proportions and strength Bones get larger/thicker when… Large muscles are attached to them Need more bone to attach the large muscle to Bones get smaller/weaker when… Physical inactivity Non-use of musclesatrophy Small muscles don’t need large bones to attach to Bones remodeled to become smaller
- 12. Long Bones Longer than wide Contain shaft with head at each end Mostly compact bone Limbs (not ankle or wrist bones) Short Bones Cube-shaped Mostly spongy bone Wrist and ankle bones Patella (kneecap) Flat Bones Thin, flat, usually curved Two layers of compact bone with spongy bone in between Skull, ribs, breastbone Irregular Bones Don’t fit into the other categories Vertebrae, hip bones
- 14. Diaphysis Shaft Made of compact bone Epiphyses Ends of long bone Made of compact bone surrounding spongy bone Covered with articular cartilage Smooth, glassy, decreases friction at joints
- 15. Epiphyseal Line ◦ Line of bone tissue that looks different from rest of bone ◦ Remnant of epiphyseal plate Hyaline cartilage Causes long bones to grow lengthwise
- 16. Periosteum ◦ Outer covering of shaft ◦ Like “skin” on chicken bone Sharpey’s fibers ◦ Attach periosteum to bone Arteries ◦ Supply nutrients to bone cells
- 17. Medullary Cavity ◦ In shaft ◦ Contains yellow marrow (adipose) in adults ◦ Contains red marrow in infants (for blood cell formation)
- 18. Osteon (Haversian system) ◦ A “unit” of bone Central (Haversian) canal ◦ Opening in center of osteon ◦ Contains blood vessels Perforating (Volkman’s) canal ◦ Perpendicular to central canal ◦ Contains blood vessels and nerves
- 20. Lacunae Cavities that contain osteocytes (bone cells) Arranged in concentric rings (like tree rings) Lamellae Rings around the central canal Where the lacunae can be found
- 21. Canaliculi ◦ Tiny canals ◦ Radiate from central canal to lacunae ◦ Transport nutrients to bone cells
- 22. The human skeleton can be divided into two ◦ The axial skeleton ◦ The appendicular skeleton. The axial skeleton is formed by the vertebral column, the rib cage, the skull and other associated bones. The appendicular skeleton, which is attached to the axial skeleton, is formed by the shoulder girdle, the pelvic girdle and the bones of the upper and lower limbs.
- 24. The core of the skeleton is referred to as the axial skeleton. It consists of the following 80 bones. The upright posture of humans is maintained by the axial skeleton, which transmits the weight from the head, the trunk, and the upper extremities down to the lower extremities at the hip joints. ◦ Skull: 22 bones ◦ Hyoid: 1 bone ◦ Vertebrae: 32 -34 bones ◦ Ribs: 24 bones ◦ Sternum: 1 bone
- 26. The skull consists of 22 bones and 7 associated bones. All the larger skull bones are shown in this exploded view. They fall into two main groups. ◦ One group (including the frontal, parietal, and temporal bones) surrounds the brain and is fused together to form the cranium. ◦ The remainder of the bones form the face. Sutures ◦ Interlocking, immovable joints holding most skullbones together Mandible-only freely movable bone in skull
- 28. This highly flexible structure, also called the vertebral column, supports the head and body. It also protects the delicate tissues of the spinal cord. It is made up of 32-34 bones called vertebrae, separated by intervertebral discs, which act as shock absorbers. The bones of the spine are kept in place and supported by attached ligaments and muscles.
- 29. Hollow portions of bone around nasal cavity ◦ Named for bones they are found in ◦ Lighten skull ◦ Amplify sounds when speaking/ give resonance
- 30. Large in comparison to body length of infant Contains fontanelles ◦ Soft fibrous membranes connecting cranial bones “Soft Spots” Usually convert to bone around 24 months after birth
- 31. Vertebrae named for their location ◦ 7 cervical vertebrae C1 = Atlas C2 = Axis ◦ 12 thoracic vertebrae ◦ 5 lumbar vertebrae ◦ Sacrum 5 fused vertebrae ◦ Coccyx 4 fused vertebrae Vertebrae separated by fibrocartilage discs ◦ Cushions/absorbs shock
- 33. Forms a cage to protect organs Three parts ◦ Sternum Flat bone 3 fused bones Manubrium Body Xyphoid process Attached to first 7 pair of ribs ◦ Rib Cage 12 pairs True Ribs= 7 pair False Ribs = 5 pair Floating Ribs = 2 pair ◦ Thoracic vertebrae
- 34. The appendicular skeleton is divided into six major regions: Pectoral girdles (4 bones) – ◦ Left and right clavicle (2) ◦ Scapula (2). Arms and forearms (6 bones) – ◦ Left and right humerus (2) (arm) ◦ Ulna (2) ◦ Radius (2) (forearm). Hands (54 bones) – ◦ Left and right carpals (16) (wrist) ◦ Metacarpals (10) ◦ Proximal phalanges (10), ◦ Intermediate phalanges (8) ◦ Distal phalanges (10) Pelvis (2 bones) – ◦ Left and right hip bone (2). Thighs and legs (8 bones) – ◦ Left and right femur (2) (thigh) ◦ Patella (2) (knee) ◦ Tibia (2) ◦ Fibula (2) (leg). Feet and ankles (52 bones) Left and right tarsals (14) (ankle) Metatarsals (10) Proximal phalanges (10) Intermediate phalanges (8) Distal phalanges (10).
- 36. Pectoral girdles (4 bones) ◦ Left and right clavicle (2) ◦ Scapula (2).
- 37. Arms and forearms (6 bones) – ◦ Left and right humerus (2) (arm) ◦ Ulna (2) ◦ Radius (2) (forearm).
- 38. Hands (54 bones) – ◦ Left and right carpals (16) (wrist) ◦ Metacarpals (10) ◦ Proximal phalanges (10), ◦ Intermediate phalanges (8) ◦ Distal phalanges (10)
- 39. Three pairs of fused bones ◦ Ilium ◦ Ischium ◦ Pubic bone Carries total weight of upper body Protects ◦ Reproductive organs ◦ Bladder ◦ Part of large intestine
- 40. Female inlet larger/more circular Female pelvis is shallower, bones lighter/thinner Female hip bones flare wider Female sacrum is shorter/less curved Female pubic arch is more rounded/angle is greater
- 41. ◦ Left and right femur (2) (thigh) ◦ Patella (2) (knee) ◦ Tibia (2) ◦ Fibula (2) (leg).
- 42. Left and right tarsals (14) (ankle) Metatarsals (10) Proximal phalanges (10) Intermediate phalanges (8) Distal phalanges (10).
- 43. Articulations of bones Functions ◦ Hold bones together ◦ Mobility Classified by structure/function Fibrous joints ◦ Immovable EX: sutures of skull Cartilaginous joints ◦ Immovable OR slightly movable EX: Pubic symphysis and Vertebrae Synovial joints ◦ Freely movable
- 44. Articulating bones separated by joint cavity ◦ Articular cartilage covers bone ends ◦ Joint surfaces enclosed by fibrous capsule ◦ Cavity contains synovial fluid ◦ Ligaments help reinforce the joint Associated Joint Structures ◦ Bursae Flat fibrous sacs Lined with synovial membrane Contains synovial fluid Common where ligaments, muscles, skin, tendons rub together ◦ Tendon sheath Elongated bursa wrapping around a tendon that deals with lots of friction Like a bun around hot dog
- 48. A break in a bone Types of Fractures ◦ Simple (closed) fracture Bone breaks cleanly, does not penetrate skin ◦ Compound (open) Fracture When bone ends penetrate through skin Treated by reduction and immobilization ◦ Realignment of bone ends
- 50. Hematoma forms Blood vessels rupture when bone breaks Blood filled swelling Cells without nutrients die Fibrocartilage callus forms Made of connective tissue Splints the break Phagocytes dispose of dead tissue Bony callus forms Osteoblasts/clasts move in, create callus of spongy bone Remodeling Osteoblasts/clasts remodel in response to stress on the bone Helps strengthen bone Creates a permanent “patch” at the site Often, a healed fracture can be stronger than the rest of the bone
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