Skeletal System Chapter 5

1. Skeletal System Chapter 5

2. The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments ( connective tissue that joins two bones) Divided into two divisions Axial skeleton Appendicular skeleton

3. Functions of Bones Support of the body Framework to support and anchor delicate organs legs support the entire body when we stand Ribs support thoracic cavity’s wall Protection of soft organs Skull protects brain Ribcage protects lungs and heart Pelvis protects reproductive organs

4. Functions of Bones Movement due to attached skeletal muscles Muscles attach to the bones by tendons Helps in the movement of the body Storage of minerals and fats Stores calcium and phosphate Calcium stored is used in muscle contraction Stores fat in the bone marrow Blood cell formation Bone marrow is the site for the synthesis of red blood cells White blood cells

5. Bone Tissues • Two basic types of bone tissue • Compact bone • Homogeneous • found in long bones • Spongy bone • Small needle-like pieces of bone • Many open spaces • found in short, irregular bones

6. Classification of Bones on the Basis of Shape The adult skeleton has 206 bones Based on the shape they are of 4 types Long bones Short bones Flat bones Irregular bones

7. Long bones Typically longer than wide Have a shaft with heads at both ends Contain mostly compact bone Examples: Femur, humerus Short bones Generally cube-shaped Contain mostly spongy bone Examples: Carpals, tarsals

8. Flat bones Thin and flattened Usually curved Sandwich of spongy bone between two layers of compact bone Examples: Skull, ribs, sternum Irregular bones Irregular shape Example: Vertebrae and hip

9. Gross Anatomy of a Long Bone Diaphysis Shaft that makes length of the bone Composed of compact bone Periosteum Outside covering of the diaphysis Made up of Fibrous connective tissue Medullary cavity Cavity of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation) in infants

10. Sharpey’s fibers Also known as perforating fibers Made of several Connective tissue fibers Help secure periosteum to underlying bone Arteries Supply bone cells with nutrients Also facilitates the repair of bones on injury

11. Epiphysis Ends of the bone Composed mostly of spongy bone Articular cartilage Covers the external surface of the epiphyses Made of hyaline cartilage Soft, slimy and smooth in texture Decreases friction at joint surfaces Epiphyseal line: Bony line that separates the epiphysis from diaphysis Seen in adult Remnant of epiphyseal plate location for bone growth in length during development made of hyaline cartilage

12. Bone Markings Surface features of bones Appear as bumps, holes, projections Sites of attachments for muscles, tendons, and ligaments Passages for nerves and blood vessels Categories of bone markings Projections and processes – grow out from the bone surface: tuberosity, tubercle, trochanter Depressions or cavities – indentations Foraman: an oval opening

13. Microscopic Anatomy of a compact Bone Very organized structures made of several units. Each unit is called Osteon (Haversian System) A functional unit of bone consisting of Central (Haversian) canal Opening in the center of an osteon Carries blood vessels and nerves Perforating (Volkman’s) canal Canal perpendicular to the central canal Carries blood vessels and nerves

14. Lamellae Rings around the central canal Sites of lacunae Lacunae Cavities containing bone cells (osteocytes) Arranged in concentric rings Canaliculi Tiny canals Radiate from the central canal to lacunae Form a transport system connecting all bone cells to a nutrient supply Bone’s hardness is the result of calcium salts Flexibility and ability to resist tension is provided by collagen fibers

15. Bone formation, growth and remodeling In embryos, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone Process of bone formation is called ossification Cartilage remains in isolated areas such as Bridge of the nose Parts of ribs Joints

16. Bone Growth Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Bone replaces cartilage In the adult bone grows in diameter It is appositional growth

17. Types of Bone Cells Osteoblasts Bone-forming cells Osteocytes Mature bone cells Osteoclasts Bone-destroying cells Break down bone matrix for remodeling and release of calcium Bone Remodeling: Old bone is replaced with new bone Osteoclasts remove old bone and osteoblast forms new bone Regulated by nutrition, hormones

18. Rickets Lack of Calcium Lack of Vitamin D Soft bones Diagnosis: bowed feet

19. Bone Fractures A break in a bone: brittle bones, falls, injuries, Types of bone fractures Closed (simple) fracture – break that does not penetrate the skin Immobilization: Cast Open (compound) fracture – broken bone penetrates through the skin Surgery to put the pieces back together by pins or wires It takes about 6-8 weeks to heal a simple fracture

20. Common Types of Fractures

21. Steps: Repair of Bone Fractures Hematoma forms: Blood vessels are ruptured, Hematoma (blood-filled swelling) forms, blood cells die due to lack of nutrients Fibrocartilage Callus: Is mass of connective tissue that forms at a fracture site and connects the broken ends of the bone Bony Callus: Callus is replaced by a bony callus with the help of osteoblasts and osteoclasts Bony callus is remodeled to form a bone

22. Skeleton System

23. Skull: total 22 bones. Attached to one another by sutures Axial Skeleton

24. Cranium: enclosing brain:made of 8 bones: 1 Frontal forms forehead and front of skull 2 temporal forms the sides and a part of the base of the skull Serves as Attachment site for mandible and cheek bone zygomatic

25. 2 Parietals forms roof and sides of the cranium 1 sphenoid: butterfly shaped forming base of the cranium, floor of the eye orbits 1 ethmoid: present between the eyes forming a part of the orbit and nasal cavity I Occipital: forms back and part of the base of the skull

26. Facial Bones :composed of 14 bones: 1 Mandible: is lower jaw, only movable bone of the skull, and all others are immovable. 2 Maxillae: forms upper jaw by joining of two bones 2 Zygomatics: are cheek bones

27. Facial Bones 2 Nasal bones Lie side by side forming bridge of the nose 2 lacrimal bones are present inside of the eye in front of the orbital cavity 2 inferior nasal conchae form the sides of the nasal cavity.

28. Facial : composed of 14 bones: 1 vomer (shaped like blade of plow forms nasal septum 2 Palatine form the back part of the hard palateand floor of nasal cavity

29. Human Skull, Superior View

30. Paranasal Sinuses Hollow portions of bones surrounding the nasal cavity Include frontal sinus, ethmoid sinus, sphenoid sinus, maxillary sinus Functions of paranasal sinuses Lighten the skull Give resonance and amplification to voice

31. The Hyoid Bone The only bone that does not articulate with another bone It hangs in the middle of the neck above larynx Attached to the temporal bone with the help of ligaments Horse shoe shaped Serves as a moveable base for the tongue Attachment site for the muscles of neck Raise and lower the larynx when we swallow and speak

32. The Fetal Skull The fetal skull is large compared to the infants total body length 1:4 Adult: 1: 8 Fontanels – fibrous membranes connecting the cranial bones Soft spots Made of cartilage Allow the brain to grow Convert to bone within 24 months after birth

33. Vertebral Column: 26 bones in the adult 34 bones in the embryonic stage Vertebrae separated by intervertebral discs Absorbs shocks and gives the spine flexibility The spine has a normal curvature Each vertebrae is given a name according to its location Cervical 7, Thoracic 12, lumbar 5, sacral 1(fused of 5) coccygeal 1(fused from 4 or 5)

34. S shape give two types of curves Primary: thoracic and sacral region Present at the time of birth Secondary : Cervical: when the baby begins to raise neck Lumbar: baby begins to walk Vertebral Column: Functions: A. Supports weight of head and trunk, B. protects spinal cord, C. allows spinal nerves to exit spinal cord, D. site of muscle attachment, E. facilitates movement of head and neck

35. Each vertebra hasBody: gives strength, Pedicles : 2 stalks arising from body. Lamina: arise as projection from each pedicle Spinous process: Lamina fuse to form spinous processTransverse process: pedicels join with lamina giving raise to transverse process-attaches to the muscles and ligaments.

36. vertebral foramina: Canal through which spinal cord passesIntervertebral discs: present between vertebra made of firbocartilage-support and prevent rubbing of 2 vertebra.Intervertebral Forman: Spinal nerves come out

39. Thoracic cage Forms a cage to protect major organs (heart, lungs) Consists of: Ribs: 12 pairs sternum (breast bone) anteriorly and thoracic vertebra (12) posteriorly.

40. Sternum: manubrium, body and xiphoid process Manubrium:The top portion Fuses with : 1. clavicle (collarbone) forming T shaped structure 2. Ribs ( first pair)laterally

41. Sternum Body: long and thin Attachment site: 2-7th pairs of ribs laterally. Xiphoid process: The tip of the sternum

42. Ribs: Total 12 pairs: 1-7 pairs of ribs : true ribs attached to sternum directly by coastal cartilage 8-12 pairs of ribs are called false ribs not attached to sternum directly or not attached to the sternum at all

43. False Ribs: 8-10 pair attach to cartilage of 7th rib 11 – 12 pair are floating ribs. Intercoastal spaces: spaces between the ribs. Intercoastal spaces are filled with intercoastal muscles – help in breathing

44. Appendicular Skeleton Consists of 126 bones Consists of the upper and lower limbs And pectoral and pelvic girdle

45. Pectoral or Shoulder Girdle These bones allow the upper limb to have exceptionally free movement Pectoral girdle:clavicle and scapula clavicle: (collar bone):S shaped bone. Attaches to manubrium of sternum medially and to scapula laterally Scapula: triangular in shape Acromium process: attaches to clavicle Coracoid process: holds the arm out (laterally) from the body, increases arm’s mobility Glenoid cavity: holds humerus

46. Upper limb is composed ofHumerus(arm)Head: fits into glenoid cavity of scapula Capitulum: articulates with radius Trochlea: articulates with ulna

47. Forearm radius (towards thumb), Lateral bone Head of radius articulates with capitulum of humerus Ulna (towards little finger), Medial Bone trochlear notch articulates with trochlea of humerus

48. Hand: carpal bones(wrist bones):8 metacarpals (palm bones):5 Phalanges (finger bones):14

49. Pelvic girdle: two coxa, sacrum fuse Coxa: known as hipbone Composed of three fused bones: Ileum ( gives shape to hip) ischium( helps in sitting) pubis(joins in front) acetabulum, is formed by joining three pelvic girdle bones Attaches to head of the femur

50. Functions of pelvic girdle: attachment of lower limb Provides base of support for body weight Protects abdominopelvic organs Protects developing fetus (in female)