Chapter 7- Skeletal System-Part 1-SR.pptx

anatomy session about the skeletal system (university level)

1. ANATOMY AND PHYSIOLOGY CHAPTER 7: SKELETAL SYSTEM-Part 1 BIO 343

2. O U TL I N E INTRODUCTION TO THE SKELETAL SYSTEM ANATOMY OF BONES/BONE TISSUE

3. INTRODUCTION TO SKELETAL SYSTEM Skeletal system —composed of bones, cartilages, and ligaments Forms strong, flexible framework of the body Osteology —the study of bone Cartilage —forerunner of most bones Tissue that c overs many joint surfaces of mature bone s Ligaments —hold bones together at the joints Tendons —attach muscle to bone © The McGraw-Hill Companies, Inc.

4. FUNCTIONS OF THE SKELETAL SYSTEM Support —holds up the body, supports muscles Protection —brain, spinal cord, heart, lungs Movement —limb movements, breathing, action of muscle on bone Electrolyte balance —calcium and phosphate ions Acid–base balance —buffers blood against excessive pH changes (CaCO 3 and phosphate help in blood acidosis) Blood formation —red bone marrow is the chief producer of blood cells

5. OVERVIEW OF THE SKELETON Axial skeleton is colored tan Forms central supporting axis of the bod y Skull , auditory ossicles , hyoid bones (anterior neck), vertebral column , and thoracic cage Appendicular skeleton is colored green Bones of upper limb and pectoral girdle Bones of the lower limb and p elvic girdle Copyright © The McGraw-Hill Companies .

6. GENERAL CLASSIFICATION OF BONES a) Long bones (ex: humerus) Longer than wide Rigid levers acted upon by muscles b) Short bones (ex: carpal of wrist) Equal in horizontal and vertical dimensions (cubed shape) Glide across one another in multiple directions c) Flat bones (ex: sternum) Protect soft organs Thin, flattened and curved d) Irregular bones (ex: vertebra) Elaborate shapes that do not fit into other categories

7. GENERAL FEATURES OF BONES Compact and spongy bone (bone tissue) D iaphysis and epiphysis Nutrient foramen P e r ios t e u m Endosteum Articular cartilage Marrow (medullary) cavity Red and yellow bone marrow Epiphyseal plate (growth plate) Epiphyseal line (a) Living ( b ) D r i e d Marrow cavity Per i o s t eu m Nu t r i en t f or a m e n Site of endosteum Compact bone Spong y bon e E p i phy si s E p i phy si s D i a phy si s A r t i c u l a r c a r t il a g e Re d bon e marrow Y e ll o w bon e m a rro w Epiphyseal line Articular cartilage The bone is a composite material —combination of two basic structural materials, a ceramic (hydroxyapatite) and a polymer (collagen). E p i phy s e a l line

8. O U TL I N E INTRODUCTION TO THE SKELETAL SYSTEM ANATOMY OF BONES/BONE TISSUE

9. ANATOMY OF A LONG BONE Compact (dense) bone —outer shell of dense white osseous tissue Spongy (cancellous) bone — more loosely organized form of osseous tissue that occupies the central space of the bone Diaphysis (shaft) —cylinder of compact bone that provide s leverage Epiphyses — expanded head at each end ; Enlarged to strengthen the joint and provide added surface area for the attachment of tendons and ligaments

10. ANATOMY OF A LONG BONE Nutrient foram en — holes in the bone surface through which blood vessels penetrate Endosteum —thin layer of reticular connective tissue lining the marrow cavity. It also lines a canal system found throughout the compact bone Periosteum —external layer of the bone except the articular cartilage. It is composed of: Outer fibrous layer of collagen Dense membrane of connective tissue containing fibroblasts that produce collagen Inner osteogenic layer of bone-forming cells Contains fibroblasts that produce cartilage cells Important to growth of bone and healing of fractures

11. ANATOMY OF A LONG BONE Articular cartilage —layer of hyaline cartilage that covers the joint surface where one bone meets another Enables joints to move more easily Medullary cavity (marrow cavity)—space in the diaphysis of a long bone that contains bone marrow Epiphyseal plate (growth plate)— area of hyaline cartilage that separates the marrow spaces of the epiphysis and diaphysis Enables growth in length Epiphyseal line —in adults, a bony scar that marks where the epiphyseal plate used to be

12. BONE MARROW Bone marrow —general term for soft tissue that occupies the marrow cavity of a long bone and small spaces amid the trabeculae of spongy bone Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1) Red marrow ( myeloid tissue ) Found i n nearly every bone in a child Hematopoietic tissue—produces blood cells and is composed of multiple tissues In adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur 2) Yellow marrow found in adults Most red marrow turns into fatty yellow m arrow in adults No longer produces blood

13. HISTOLOGY OF OSSEOUS TISSUE Compact bone Spongy bone Bone marrow Trabecula Lacunae Canaliculi Central canal Lamella Compact and spongy bone in a longitudinal section of the femur Histology of decalcified spongy bone and red bone marrow Microscopic appearance of a cross section of an osteon of dried compact bone 20 µm Compact bone Has onion-like concentric lamellae layers of matrix arranged around a central canal Lamella layers are connected with each other by canaliculi A central canal and its lamella constitute an osteon ꟷ the basic structural unit of a compact bone Spongy bone Consists of a lattice of delicate slivers called trabeculae Covered with endosteum and permeated by spaces filled with bone marrow The matrix is arranged in lamellae like those of compact bone, but there are few osteons © McGraw-Hill Companies

14. BONE TISSUE: THE MATRIX Matrix of osseous tissue is, by dry weight, about 1/3 organic and 2/3 inorganic matter Organic matter Collagen, carbohydrate–protein complexes, such as glycosaminoglycans , proteoglycans, and glycoproteins Provide flexibility to the bones Inorganic matte r 85% hydroxyapatite (crystallized calcium phosphate salt) 10% calcium carbonate Other minerals (fluoride, sodium, potassium, magnesium) Provide hardness to the bones

15. BONE CELLS Four principal types of bone cells : Osteogenic cells O steoblasts O steocytes O steoclasts Bone Cells and Their Development. (a) Osteogenic cells give rise to osteoblasts, which deposit matrix around themselves and transform into osteocytes. (b) Bone marrow stem cells fuse to form osteoclast. © McGraw-Hill Companies

16. BONE CELLS 1) Osteogenic cells — stem cells that a rise from embryonic mesenchymal cells ; multiply continuously to produce new osteoblasts 2) Osteoblasts — bone-forming cells that synthesize the organic matter Line up as single layer of cells under endosteum and periosteum They are n onmitotic ; They originate from osteogenic cells Secrete a hormone called osteocalcin , which: Stimulates insulin secretion of pancreas Increases insulin sensitivity in adipocytes which limit the growth of adipose tissue

17. BONE CELLS 3) Osteocytes — former osteoblasts that have become trapped in the matrix they have deposited Reside in lacunae Some osteocytes reabsorb bone matrix while others deposit it Contribute to homeostatic mechanism of bone density and calcium and phosphate ions When stressed, they produce biochemical signals that regulate bone remodeling 4) Osteoclasts — bone-dissolving cells found on the bone surface Have a d ifferent origin from the rest of bone cells They develop from the same bone marrow stem cells that give rise to blood cells Are u nusually large cells formed from the fusion of several stem cells Typically have 3 to 4 nuclei, may have up to 50 Ruffled border to increase surface area

18. BONE FORMATION The formation of bone is called ossification or osteogenesis There are two methods of ossification: Intramembranous : produces the flat bones of the skull, most of the clavicle (bone between sternum and shoulder blade), and part of the mandible (bone of lower jaw). Cartilage is not present during this process. Endochondral : process in which a bone develops from a preexisting model composed of cartilage. Most bones of the body develop in this way. Intramembranous ossification in the fetal cranium. © McGraw-Hill Early cartilage model © McGraw-Hill

19. BONE FORMATION Bone formation occurs in four principal situations: (1) the initial formation of bones in an embryo and fetus , (2) the growth of bones during infancy, childhood, and adolescence until their adult sizes are reached, (3) the remodeling of bone (replacement of old bone by new bone tissue throughout life), and (4) the repair of fractures (breaks in bones) throughout life Fetal skeleton at 12 weeks of age. Red-stained regions are calcified, while the remaining translucent part is still composed of cartilage. © McGraw-Hill

20. Ossification doesn’t end at birth, but continues throughout life with the growth and remodeling of bones Bones grow in two directions : Length Width BONE GROWTH BONE ELONGATION BONE WIDENING

21. BONE ELONGATION The e piphyseal plat e f unctions as growth zone where the bones elongate Consists of typical hyaline cartilage in the middle , w ith a transition zone on each side where cartilage is being replaced by bone Metaphysis is the zone of transition facing the marrow cavity © McGraw-Hill

22. X-RAY OF A CHILD’S HAND The cartilaginous epiphysial plates are evident at the ends of the long bones Long bones of the hand and fingers develop only one epiphysial plate © McGraw-Hill

23. BONE WIDENING AND THICKENING Bones also continually grow in diameter and thickness This involves a process called appositional growth Occurs by intramembranous ossification at the bone surface Osteoblasts on deep side of the periosteum deposit osteoid tissue on the bone surface Lay down matrix in layers parallel to the surface This process produces the surface layers of bone called circumferential lamellae

24. BONE REMODELING In addition to their growth, bones are continually remodeled throughout life by the absorption of old bone and the deposition of new one This process replaces ~10% of the skeletal tissue per year Wolff’s law of bone: the architecture of a bone is determined by the mechanical stresses placed upon it, and the bone thereby adapts to withstand it Remodeling is a collaborative and precise action of osteoblasts and osteoclasts If a bone is little used, osteoclasts remove matrix and get rid of unnecessary mass. If a bone is heavily used or a stress is consistently applied to a particular region of a bone, osteoblasts deposit new osseous tissue and thicken the bone

25. ACHONDROPLASTIC DWARFISM Occurs due to spontaneous mutations of the DNA Due to failure of cartilage growth Long bones of the limbs stop growing in childhood Growth of other bones is unaffected Individuals with this condition have a short stature, but a normal-size head and trunk © McGraw-Hill