Anatomy of Human Bone Structure | PDF

Figure 7.30 Herniated Nucleus Pulposus (HNP) Weakening of the anulus fibrosus can result in herniation (protrusion) of the nucleus pulposus and compression of a spinal nerve (or less commonly the spinal cord), resulting in pain and/or muscle weakness in the body regions supplied by that nerve. F...

Figure 7.30 Herniated Nucleus Pulposus (HNP) Weakening of the anulus fibrosus can result in herniation (protrusion) of the nucleus pulposus and compression of a spinal nerve (or less commonly the spinal cord), resulting in pain and/or muscle weakness in the body regions supplied by that nerve. Figure 7.24 Intervertebral Disc The bodies of adjacent vertebrae are separated and united by an intervertebral disc, which provides padding and allows for movements between adjacent vertebrae. The disc consists of a fibrous outer layer called the anulus fibrosus and a gel-like center called the nucleus pulposus. The intervertebral foramen is the opening formed between adjacent vertebrae for the exit of a spinal nerve. Figure 7.21 Abnormal Curvatures of the Vertebral Column 1. Scoliosis is an abnormal lateral bending of the vertebral column. 2. An excessive curvature of the upper thoracic vertebral column is called excessive kyphosis. 3. Excessive lordosis can be found in the lumbar region of the vertebral column. Figure 7.2 Axial and Appendicular Skeleton The axial skeleton supports the head, neck, back, and chest and thus forms the vertical axis of the body. It consists of the skull, vertebral column (including the sacrum and coccyx), and the thoracic cage, formed by the ribs and sternum. The appendicular skeleton is made up of all bones of the upper and lower limbs. What’s another name for appendages? What does the abbreviation RUE mean? Table 6.1 Bone Markings (2 of 2) © 2013 Pearson Education, Inc. Table 6.1 Bone Markings (1 of 2) Treating Osteoporosis and Osteopenia (precursor) Calcium, Vitamin D Weight-bearing exercise Hormone replacement therapy ○ Slows bone loss ○ Controversial due to increased risk of heart attack, stroke, breast cancer ○ Estrogenic compounds in soy © 2013 Pearson Education, Inc. Insufficient exercise to stress bones Diet poor in calcium and protein Smoking Hormone-related conditions ○ Hyperthyroidism ○ Low blood levels of thyroid-stimulating hormone ○ Diabetes mellitus Immobility Males with prostate cancer taking androgen-suppressing drugs The female athlete triad is an interrelationship of menstrual dysfunction, low energy availability (with or without an eating disorder), and decreased bone mineral density; it is relatively common among young women participating in sports.-NIH © 2013 Pearson Education, Inc. Homeostatic Imbalances Osteoporosis ○ Bone resorption outpaces deposit ○ Spongy bone of spine and neck of femur most susceptible Vertebral and hip fractures common © 2013 Pearson Education, Inc. Osteosarcoma Most common type bone cancer Often affects teenage boys during “growth spurt”- cells at epiphyseal plate Common in knees, long bones Presents as pain, soreness, lump Treatments: removal of part of bone, chemotherapy © 2013 Pearson Education, Inc. Osteomyelitis: Bacterial infection of the bone Pain, tenderness, lump, redness, puss Treatment with antibiotics, surgery © 2013 Pearson Education, Inc.  Rickets (osteomalacia of children) ○ Bowed legs and other bone deformities ○ Bones ends enlarged and very long ○ Cause: Vitamin D deficiency or insufficient dietary calcium © 2013 Pearson Education, Inc. Osteomalacia  ○ Bones poorly mineralized ○ Calcium salts not adequate ○ Soft, weak bones ○ Pain upon bearing weight © 2013 Pearson Education, Inc. Serotonin ○ Neurotransmitter regulates mood and sleep ○ Secreted into blood after eating Interferes with osteoblast activity Serotonin reuptake inhibitors (Prozac) cause lower bone density © 2013 Pearson Education, Inc. Calcium Homeostasis Changes in blood calcium are dangerous ○ Severe neuromuscular problems Hyperexcitability (levels too low) Nonresponsiveness (levels too high) ○ Hypercalcemia Sustained high blood calcium levels Deposits of calcium salts in blood vessels, kidneys can interfere with function © 2013 Pearson Education, Inc. Importance of Calcium Functions in ○ Nerve impulse transmission ○ Muscle contraction ○ Blood coagulation ○ Secretion by glands and nerve cells ○ Cell division 1200 – 1400 grams of calcium in body ○ 99% as bone minerals ○ Intestinal absorption requires Vitamin D © 2013 Pearson Education, Inc. Control of Remodeling Occurs continuously but regulated by genetic factors and two control loops: Negative feedback hormonal loop for Ca2+ homeostasis ○ Controls blood Ca2+ levels; Not bone integrity Responses to mechanical and gravitational forces © 2013 Pearson Education, Inc. Bone Homeostasis: Bone Remodeling Both bone deposit and bone resorption At surfaces of periosteum and endosteum Remodeling units: osteoblasts and osteoclasts © 2013 Pearson Education, Inc. Hormonal Regulation of Bone Growth Growth hormone ○ Most important in stimulating epiphyseal plate activity in infancy and childhood Thyroid hormone ○ Modulates activity of growth hormone Testosterone and estrogens at puberty ○ Promote adolescent growth spurts ○ End growth by inducing epiphyseal plate closure © 2013 Pearson Education, Inc. Figure 6.21  Stages in Fracture Repair The healing of a bone fracture follows a series of progressive steps: (a) A fracture hematoma forms. (b) Internal and external calli form. (c) Cartilage of the calli is replaced by trabecular bone. (d) Remodeling occurs. Timelines vary 4-20 weeks (6-8 most common), up to 10% nonunion or malunion. Skin is penetrated: ○ Open (compound) - skin is penetrated ○ Closed (simple) – skin is not penetrated © 2013 Pearson Education, Inc. Completeness: ○ Complete—fractured all the way through ○ Incomplete—not fractured all the way through © 2013 Pearson Education, Inc. Three Fracture Classification Position: ○ Nondisplaced—ends retain normal position ○ Displaced—ends out of normal alignment © 2013 Pearson Education, Inc. Figure 6.20 Types of Fractures Compare healthy bone with different types of fractures: 1. closed fracture, 2. open fracture, 3. transverse fracture, 4. spiral fracture, 5. comminuted fracture, 6. impacted fracture, 7. greenstick fracture, and 8. oblique fracture. Hematopoietic Tissue in Bones Red marrow ○ Found within trabecular cavities of spongy bone and flat bones ○ In medullary cavities and spongy bone of newborns ○ Adult long bones have little red marrow Heads of femur and humerus only © 2013 Pearson Education, Inc.  Near end of adolescence chondroblasts divide less often and epiphyseal plate thins then is replaced by bone Epiphyseal plate closure ○ Bone lengthening ceases ○ Bone of epiphysis and diaphysis fuses ○ Females –18 years Males – 21 years © 2013 Pearson Education, Inc. Growth of Cartilage Appositional growth ○ Cells secrete matrix against external face of existing cartilage © 2013 Pearson Education, Inc. Figure 6.18 Longitudinal Bone Growth The epiphyseal plate is responsible for longitudinal bone growth. Figure 6.17  Endochondral Ossification Endochondral ossification follows five steps. 1. Mesenchymal cells differentiate into chondrocytes. 2. The cartilage model of the future bony skeleton and the perichondrium form. 3. Capillaries penetrate cartilage. Perichondrium transforms into periosteum. Periosteal collar develops. Primary ossification center develops. 4. Cartilage and chondrocytes continue to grow at ends of the bone. 5. Secondary ossification centers develop. 6. Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage. Figure 6.14  Paget's Disease Normal leg bones are relatively straight, but those affected by Paget’s disease are porous and curved. Unknown cause, appears to be genetically linked, more common in males of Western European descent. Figure 6.12 Diagram of Compact Bone 1. This cross-sectional view of compact bone shows the basic structural unit, the osteon. 2. In this micrograph of the osteon, you can clearly see the concentric lamellae and central canals. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Figure 6.11 Bone Cells Four types of cells are found within bone tissue. Osteogenic cells are undifferentiated and develop into osteoblasts. When osteoblasts get trapped within the calcified matrix, their structure and function changes, and they become osteocytes. Osteoclasts develop from monocytes and macrophages and differ in appearance from other bone cells. Figure 6.10 Bone Features The surface features of bones depend on their function, location, attachment of ligaments and tendons, or the penetration of blood vessels and nerves. Wolff’s law: bone in a healthy animal will adapt to the loads under which it is placed. If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. What happens when loads decrease?  What environments lead to reduced load? Compact (cortical) ○ Dense outer layer; smooth and solid Spongy (cancellous or trabecular) ○ Honeycomb of flat pieces of bone deep to compact called trabeculae © 2013 Pearson Education, Inc. Figure 6.8 Periosteum and Endosteum The periosteum forms the outer surface of bone, and the endosteum lines the medullary cavity. Figure 6.7 Anatomy of a Long Bone A typical long bone shows the gross anatomical characteristics of bone. Functions of Bones 6. Triglyceride (fat) storage in bone cavities 7. Hormone production ○ Osteocalcin: Regulates bone formation © 2013 Pearson Education, Inc. Functions of Bones 4. Mineral and growth factor storage ○ Calcium and phosphorus, growth factors 5. Blood cell formation (hematopoiesis) in red marrow cavities © 2013 Pearson Education, Inc. Functions of Bones 1. Support ○ For body and soft organs 2. Protection ○ For brain, spinal cord, and vital organs 3. Movement ○ Levers for muscle action © 2013 Pearson Education, Inc.