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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Tissue Primary germ layers: ectoderm, mesoderm, and endoderm.

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Presentation on theme: "Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Tissue Primary germ layers: ectoderm, mesoderm, and endoderm."— Presentation transcript:

1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Tissue Primary germ layers: ectoderm, mesoderm, and endoderm Three layers of cells formed early in embryonic development Specialize to form the four primary tissues Nerve tissue arises from ectoderm

2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Tissue Muscle, connective tissue, endothelium, and mesothelium arise from mesoderm Most mucosae arise from endoderm Epithelial tissues arise from all three germ layers Figure 4.13

3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Skeletal Cartilage Contains no blood vessels or nerves Surrounded by the perichondrium (dense irregular CT) that resists outward expansion Three types – hyaline, elastic, and fibrocartilage

4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings BONES and SKELETAL TISSUE

5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bones and Cartilages of the Human Body Figure 6.1

6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Function of Bones Support – form the framework that supports the body and cradles soft organs Protection – provide a protective case for the brain, spinal cord, and vital organs Movement – provide levers for muscles Mineral storage – reservoir for minerals, especially calcium and phosphorus Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Reminder -Structure of Long Bone Figure 6.3a, c

8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Reminder- Structure of Short, Irregular, and Flat Bones Figure 6.4

9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Location of Hematopoietic Tissue (Red Marrow) In infants Found in the medullary cavity and all areas of spongy bone In adults Found in the spongy bone of flat bones, and the head of the femur and humerus

10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chemical Composition of Bone: Organic Osteoblasts – bone-forming cells Osteocytes – mature bone cells Osteoclasts – large cells that resorb or break down bone matrix Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chemical Composition of Bone: Inorganic Hydroxyapatites, or mineral salts Sixty-five percent of bone by mass Mainly calcium phosphates Responsible for bone hardness and its resistance to compression

12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Development Osteogenesis and ossification – the process of bone tissue formation, which leads to: The formation of the bony skeleton in embryos Bone growth until early adulthood Bone thickness, remodeling, and repair

13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Formation of the Bony Skeleton Begins at week 8 of embryo development Intramembranous ossification – bone develops from a fibrous membrane Endochondral ossification – bone forms by replacing hyaline cartilage

14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Postnatal Bone Growth Growth in length of long bones Cartilage on the side of the epiphyseal plate closest to the epiphysis is relatively inactive Cartilage abutting the shaft of the bone organizes into a pattern that allows fast, efficient growth

15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Long Bone Growth and Remodeling Growth in length – cartilage continually grows and is replaced by bone as shown Remodeling – bone is resorbed and added by appositional growth as shown Figure 6.10

16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings During infancy and childhood, epiphyseal plate activity is stimulated by growth hormone During puberty, by testosterone and estrogens Initially promote adolescent growth spurts Cause masculinization and feminization of specific parts of the skeleton Later induce epiphyseal plate closure, ending longitudinal bone growth Hormonal Regulation of Bone Growth During Youth

17 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Remodeling Remodeling units – adjacent osteoblasts (deposit) and osteoclasts (resorb) bone at periosteal and endosteal surfaces

18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Deposition Occurs where bone is injured or added strength is needed Requires a diet rich in protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese Alkaline phosphatase is essential for mineralization of bone Sites of new matrix deposition are revealed by: Osteoid seam – unmineralized band of bone matrix Calcification front – abrupt transition zone between the osteoid seam and the older mineralized bone

19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Resorption Accomplished by osteoclasts Resorption bays – grooves formed by osteoclasts as they break down bone matrix Resorption involves osteoclast secretion of: Lysosomal enzymes that digest organic matrix Acids that convert calcium salts into soluble forms Dissolved matrix is transcytosed across the osteoclasts cell where it is secreted into the interstitial fluid and then into the blood

20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Importance of Ionic Calcium in the Body Calcium is necessary for: Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division

21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Control of Remodeling Two control loops regulate bone remodeling Hormonal mechanism that maintains calcium homeostasis in the blood Mechanical and gravitational forces acting to the skeleton

22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hormonal Mechanism Rising blood Ca 2+ levels trigger the thyroid to release calcitonin Calcitonin stimulates calcium salt deposit in bone Figure 6.11

23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Hormonal Mechanism Falling blood Ca 2+ levels signal the parathyroid glands to release PTH PTH signals osteoclasts to degrade bone matrix and release Ca 2+ into the blood Figure 6.11

24 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Response to Mechanical Stress Wolffs law – a bone grows or remodels in response to the forces or demands placed upon it Figure 6.12

25 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Response to Mechanical Stress Observations supporting Wolffs law include: Long bones are thickest midway along the shaft (where bending stress is greatest) Curved bones are thickest where they are most likely to buckle Figure 6.12

26 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Response to Mechanical Stress Large, bony projections occur where heavy, active muscles attach Figure 6.12

27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Fractures (Breaks) Bone fractures are classified by: The position of the bone ends after fracture Completeness of the break The orientation of the bone to the long axis Whether or not the bones ends penetrate the skin

28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Types of Bone Fractures Learn table with fracture types 6.2?

29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Hematoma formation Torn blood vessels hemorrhage A mass of clotted blood (hematoma) forms at the fracture site Site becomes swollen, painful, and inflamed Figure

30 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Fibrocartilaginous callus forms Granulation tissue (soft callus) forms a few days after the fracture Capillaries grow into the tissue and phagocytic cells begin cleaning debris Figure

31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Bony callus formation New bone trabeculae appear in the fibrocartilaginous callus Fibrocartilaginous callus converts into a bony (hard) callus Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later Figure

32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Bone remodeling Excess material on the bone shaft exterior and in the medullary canal is removed Compact bone is laid down to reconstruct shaft walls Figure

33 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Homeostatic Imbalances Osteomalacia Bones are inadequately mineralized causing softened, weakened bones Main symptom is pain when weight is put on the affected bone Caused by insufficient calcium in the diet, or by vitamin D deficiency

34 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Homeostatic Imbalances Rickets Bones of children are inadequately mineralized causing softened, weakened bones Bowed legs and deformities of the pelvis, skull, and rib cage are common Caused by insufficient calcium in the diet, or by vitamin D deficiency

35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Homeostatic Imbalances Osteoporosis Group of diseases in which bone reabsorption outpaces bone deposit Spongy bone of the spine is most vulnerable Occurs most often in postmenopausal women Treatment Calcium and vitamin D supplements Increased weight bearing exercise Hormone (estrogen) replacement therapy (HRT) Prevented or delayed by sufficient calcium intake and weight-bearing exercise

36 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pagets Disease Characterized by excessive bone formation and breakdown Pagetic bone with an excessively high ratio of woven to compact bone is formed Pagetic bone, along with reduced mineralization, causes spotty weakening of bone Osteoclast activity wanes, but osteoblast activity continues to work

37 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Bones Mesoderm gives rise to embryonic mesenchymal cells, which produce membranes and cartilages that form the embryonic skeleton The embryonic skeleton ossifies in a predictable timetable that allows fetal age to be easily determined from sonograms At birth, most long bones are well ossified (except for their epiphyses)

38 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Bones By age 25, nearly all bones are completely ossified In old age, bone resorption predominates A single gene that codes for vitamin D docking determines both the tendency to accumulate bone mass early in life, and the risk for osteoporosis later in life

39 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Joints (Articulations) Weakest parts of the skeleton Articulation – site where two or more bones meet Functions Give the skeleton mobility Hold the skeleton together

40 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Classification of Joints: Structural Structural classification focuses on the material binding bones together and whether or not a joint cavity is present The three structural classifications are: Fibrous Cartilaginous Synovial

41 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Classification of Joints: Functional Functional classification is based on the amount of movement allowed by the joint The three functional class of joints are: Synarthroses – immovable Amphiarthroses – slightly movable Diarthroses – freely movable

42 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.11c Example - Synovial Joints: Major Ligaments and Tendons (Anterior View)

43 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Inflammatory and Degenerative Conditions Bursitis An inflammation of a bursa, usually caused by a blow or friction Symptoms are pain and swelling Treated with anti-inflammatory drugs; excessive fluid may be aspirated Tendonitis Inflammation of tendon sheaths typically caused by overuse Symptoms and treatment are similar to bursitis

44 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Arthritis More than 100 different types of inflammatory or degenerative diseases that damage the joints Most widespread crippling disease in the U.S. Symptoms – pain, stiffness, and swelling of a joint Acute forms are caused by bacteria and are treated with antibiotics Chronic forms include osteoarthritis, rheumatoid arthritis, and gouty arthritis

45 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Osteoarthritis (OA) Most common chronic arthritis; often called wear- and-tear arthritis Affects women more than men 85% of all Americans develop OA More prevalent in the aged, and is probably related to the normal aging process

46 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Osteoarthritis: Treatments OA is slow and irreversible Treatments include: Mild pain relievers, along with moderate activity Magnetic therapy Glucosamine sulfate decreases pain and inflammation SAM-e (s-adenosylmethionine) builds up cartilage matrix and regenerates tissue

47 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rheumatoid Arthritis (RA) Chronic, inflammatory, autoimmune disease of unknown cause, with an insidious onset Usually arises between the ages of 40 to 50, but may occur at any age Signs and symptoms include joint tenderness, anemia, osteoporosis, muscle atrophy, and cardiovascular problems The course of RA is marked with exacerbations and remissions

48 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rheumatoid Arthritis: Course RA begins with synovitis of the affected joint Inflammatory blood cells migrate to the joint, causing swelling Inflamed synovial membrane thickens into a pannus Pannus erodes cartilage, scar tissue forms, articulating bone ends connect The end result, ankylosis, produces bent, deformed fingers

49 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rheumatoid Arthritis: Treatment Conservative therapy – aspirin, long-term use of antibiotics, and physical therapy Progressive treatment – anti-inflammatory drugs or immunosuppressants The drug Embrel, a biological response modifier, removes cells that promote inflammation

50 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Gouty Arthritis Deposition of uric acid crystals in joints and soft tissues, followed by an inflammation response Typically, gouty arthritis affects the joint at the base of the great toe In untreated gouty arthritis, the bone ends fuse and immobilize the joint Treatment – colchicine, nonsteroidal anti- inflammatory drugs, and glucocorticoids

51 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Developmental Aspects of Joints By embryonic week 8, synovial joints resemble adult joints Few problems occur until late middle age Advancing years take their toll on joints including: Ligaments and tendons shorten and weaken Intervertebral discs become more likely to herniate OA is inevitable, and all people of 70 have some degree of OA Prudent exercise (especially swimming) that coaxes joints through their full range of motion is key to postponing joint problems

52 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sprains The ligaments (bone to bone) reinforcing a joint are stretched or torn Partially torn ligaments slowly repair themselves Completely torn ligaments require prompt surgical repair

53 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cartilage Injuries The snap and pop of overstressed cartilage Common aerobics injury Repaired with arthroscopic surgery

54 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Dislocations Occur when bones are forced out of alignment Usually accompanied by sprains, inflammation, and joint immobilization Caused by serious falls and are common sports injuries Subluxation – partial dislocation of a joint


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