1 Skeletal System

2 The skeletal system is composed of 206 bones.The skeletal system provides 1.) protection 2.)support 3.) production of red blood cells 4.) movement 5.) Triglyceride Storage (yellow fat) 6.) Storing Minerals Bones are attached to other bones by ligaments.

3 Axial Skeleton Skull, Vertebral Column, Ribs, & Sternum80 bones

4 Skull Skull 29 bones Cranium 8 Occipital 1 Temporal 2 Frontal 1Parietal 2 Sphenoid 2 Butterfly shaped or winged shaped

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7 Face 14 Mandible 1 Maxillae 2 Zygomatic 2 Lacrimal 2 Ethmoid 2

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9 Vertebral column 26 bones24 vertebrae & 1 sacrum & 1 coccyx 7 Cervical Vertebrae Atlas 1st cervical vertebrae (nod yes) Axis 2nd cervical vertebrae ( no )

10 Vertebral Column Sacrum (5) Coccyx (4) Cervical Vertebrae (7) Thoracic Vertebrae (12) Lumbar Vertebrae (5)

11 Cervical Vertebrae C1 & C2Axis Dens Atlas Body Transverse Foramen Vertebral Foramen Spinous Process

12 12 Thoracic Vertebrae 5 Lumbar Vertebrae  Hyoid Sternum & ribs 26 bones

13 Thoracic Vertebra Body Superior Articular Process Rib Facet Transverse Process Spinous Process

14 Lumbar Vertebra Body Transverse Process Pedicle Spinous Process Superior Articular Process

15 Sacrum Ala Sacral Canal Median Sacral Crest Posterior Sacral Foramen Lateral Sacral Crest

16 Ribs Composed of 12 pairs (24 bones) and the SternumThe ribs are shaped like crescents, with one end flattened and the other end rounded. The rounded ends are attached at joints to the thoracic vertebrae at the back and the flattened ends come together at the sternum, in the front. The upper seven pairs of ribs attach to the sternum with costal cartilage and are known as “true ribs.

17 Ribs The 8th through 10th ribs have non-costal cartilage which connects them to the ribs above. The last two ribs are called “free ribs” because they do not attach to the sternum or to other ribs and simply “hang free.” The length of each rib increases from number one to seven and then decreases until rib pair number 12. The first rib is the shortest, broadest, flattest, and most curved.

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19 Rib Sternal End Angle Tubercle Neck Head

20 Sternum Angle Manubrium Clavicular Notch Body Sternal Notch What is missing? Xiphoid Process

21 Appendicular Skeleton 126 bonesPectoral Girdle & upper extremities 64 bones Clavicle 2 Scapula 2 Humerus 2 Radius 2 Ulna 2 Carpals 16 Metacarpals 10 Phalanges 28

22 Lower Extremities 62 bonesCoxal Bones 3 Ilium, ischium and pubis Femur 2 Tibia 2 Fibula 2 Tarsals 14

23 Terminology: Articulating Surface: These are the areas of the bone that move in conjunction with another bone. Condyle: Rounded projection for articulation with another bone.  Head: A portion of the bone that expands beyond its constricted neck.

24 Non-articulating Surfaces: Serve as attachment sightsProjections 1. Tuberosity : a large roughened projection 2. Tubercle: a small rounded projection 3. Spine: a sharp projection 4. Crest: a ridge 5. Process: an obvious portion that protrudes from a surface. 6. Trochanter: a prominent process.

25 Depressions 1. Fossa Shallow or hollow bone depression 2. Groove: long shallow depression 3.Foramen: a hole 4. Sinus: an air filled cavity 5. Meatus: a tube shaped opening

26 Bone Structure: Diaphysis: The shaft of a long bone.Diaphysis: The shaft of a long bone. Epiphysis: Two enlarge ends of the bones Proximal Epiphysis and Distal Epiphysis Proximal Epiphysis contains the red bone marrow in adult bones.

27 Pelvic Girdle

28 Pelvic girdle Ilium: The larger, superior Portion of the pelvic region. ( Hip bone) Iliac Crest: Rim of the ilium or hip. Iliac fossa the depression of the ilium. Ilium is fused to the Sacrum by the sacroiliac joint.

29 Ischium: The inferior and posterior portion of the hip.Pubis: The inferior and anterior portion of the Subpubic angle: male is more straight thanfemal skeloton. Obturator Foramen: filled with connective tissue. Symphysis pubis: joins the right and left halves. Acetabulum: piont of articulation of the lower limb and the pelvic girdle.

30 Sacrum Ilium Iliac Fossa Pelvic Brim Acetabulum Obturator Foraman Ischium Pubis Pubic Symphasis Pelvis

31 Coxal Bone Iliac Crest Posterior Superior Iliac Spine Anterior Superior Iliac Spine Anterior Inferior Iliac Spine Posterior Inferior Iliac Spine Acetabulum Greater Sciatic Notch Obturator Foramen Ischial Tuberosity Ischial Spine

32 Femur Greater Trochanter Lateral Epicondyle Head Lesser TrochanterMedial Epicondyle

33 Femur posterior Lesser Trochanter Gluteal Tuberosity Medial EpicondyleLinea Aspera Medial Condyle Head Lateral Condyle Greater Trochanter Lateral Epicondyle

34 Tibia Medial Malleolus Anterior Tibial Crest Tibial Tuberosity PatellaMedial Condyle Lateral Condyle

35 Fibula Lateral Malleolus Head

36 Proximal Phalanx Middle Phalanx 5 4 Distal Phalanx 3 2 1 Proximal Phalanx Tarsals Metatarsals Phalanges Foot

37 Cuboid Calcaneous Talus 1st Cuneiform 3rd Cuneiform Navicular 2nd Cuneiform Foot - Tarsals

38 Bones Of the Upper Extremities.Humerus Scapula Clavicle Radius Ulnu Carples Metacarples Phalangees.

39 Posterior Scapula Supraspinous Fossa Scapular Spine Scapula AcromionInfraspinous Fossa

40 Anterior Scapula Coracoid Process Glenoid Cavity Subscapular Fossa

41 Clavicle (inferior view)Sternal End Acromial End Conoid Tubercle

42 Humerus – Anterior ViewIntertubercular Groove Lateral Epicondyle Greater Tubercle Capitulum Coronoid Fossa Trochlea Medial Epicondyle Lesser Tubercle Deltoid Tuberosity

43 Humerus – Posterior ViewHead Olecranon Fossa Greater Tubercle Medial Epicondyle Trochlea Lateral Epicondyle

44 Ulna Coronoid Process Olecranon Process Trochlear Notch Radial NotchStyloid Process Head

45 Radius Radial Tuberosity Head Styloid Process

46 Hand and Wrist Middle Phalanx Distal Phalanx Proximal PhalanxPhalanges Distal Phalanx 3 Metacarpals 5 4 2 1 Carpals Proximal Phalanx

47 Bone Structure Bones are organs. Thus, they’re composed of multiple tissue types. Bones are composed of: Bone tissue (a.k.a. osseous tissue). Fibrous connective tissue. Cartilage. Vascular tissue. Lymphatic tissue. Adipose tissue. Nervous tissue.

48 Bone is an extremely dynamic tissue!!!!All bones consist of a dense, solid outer layer known as compact bone and an inner layer of spongy bone – a honeycomb of flat, needle-like projections called trabeculae. Bone is an extremely dynamic tissue!!!! Above: Note the relationship btwn the compact and spongy bone. Below: Close up of spongy bone.

49 Note the gross differences between the spongy bone and the compact bone in the above photo.Do you see the trabeculae?

50 Bone Tissue Bone tissue is a type of connective tissue, so it must consist of cells plus a significant amount of extracellular matrix. Bone cells: Osteoblasts Bone-building cells. Synthesize and secrete collagen fibers and other organic components of bone matrix. Initiate the process of calcification. Found in both the periosteum and the endosteum The blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.

51 Bone Structure 2. Osteocytes Mature bone cells.Yellow arrows indicate osteocytes – notice how they are surrounded by the pinkish bone matrix. Blue arrow shows an osteoblast in the process of becoming an osteocyte. 2. Osteocytes Mature bone cells. Osteoblasts that have become trapped by the secretion of matrix. No longer secrete matrix. Responsible for maintaining the bone tissue. On the right, notice how the osteocyte is “trapped” within the pink matrix

52 3. Osteoclasts Huge cells derived from the fusion of as many as 50 monocytes (a type of white blood cell). Cells that digest bone matrix – this process is called bone resorption and is part of normal bone growth, development, maintenance, and repair. Concentrated in the endosteum. On the side of the cell that faces the bone surface, the PM is deeply folded into a ruffled border. Here, the osteoclast secretes digestive enzymes (how might this occur?) to digest the bone matrix. It also pumps out hydrogen ions (how might this occur?) to create an acid environment that eats away at the matrix. What advantage might a ruffled border confer? Why do we want a cell that eats away at bone? (Hint: bone is a very dynamic tissue.)

53 Here, we see a cartoon showing all 3 cell typesHere, we see a cartoon showing all 3 cell types. Osteoblasts and osteoclasts are indicated. Note the size of the osteoclast (compare it to the osteoblast), and note the ruffled border. Why is there a depression underneath the osteoclast? What is the name of the third cell type shown here? What do you think the tan material represents?

54 Bone Structure Bone Matrix:Consists of organic and inorganic components. 1/3 organic and 2/3 inorganic by weight. Organic component consists of several materials that are secreted by the osteoblasts: Collagen fibers and other organic materials These (particularly the collagen) provide the bone with resilience and the ability to resist stretching and twisting.

55 Inorganic component of bone matrixThree-dimensional array of collagen molecules. The rod-shaped molecules lie in a staggered arrangement which acts as a template for bone mineralization. Bone mineral is laid down in the gaps. Inorganic component of bone matrix Consists mainly of 2 salts: calcium phosphate and calcium hydroxide. These 2 salts interact to form a compound called hydroxyapatite. Bone also contains smaller amounts of magnesium, fluoride, and sodium. These minerals give bone its characteristic hardness and the ability to resist compression. Note collagen fibers in longitudinal & cross section and how they occupy space btwn the black bone cells.

56 This bone: a. Has been demineralized b. Has had its organic component removed

57 Long Bone Structure Shaft plus 2 expanded ends.Shaft is known as the diaphysis. Consists of a thick collar of compact bone surrounding a central marrow cavity In adults, the marrow cavity contains fat - yellow bone marrow. Expanded ends are epiphyses Thin layer of compact bone covering an interior of spongy bone. Joint surface of each epiphysis is covered w/ a type of hyaline cartilage known as articular cartilage. It cushions the bone ends and reduces friction during movement.

58 Bone Marrow Bone marrow is a general term for the soft tissue occupying the medullary cavity of a long bone, the spaces amid the trabeculae of spongy bone, and the larger haversian canals. There are 2 main types: red & yellow. Red bone marrow = blood cell forming tissue = hematopoietic tissue Red bone marrow looks like blood but with a thicker consistency. It consists of a delicate mesh of reticular tissue saturated with immature red blood cells and scattered adipocytes. Notice the red marrow and the compact bone

59 Distribution of MarrowNote the compact bone on the bottom and marrow on the bottom. In a child, the medullary cavity of nearly every bone is filled with red bone marrow. In young to middle-aged adults, the shafts of the long bones are filled with fatty yellow bone marrow. Yellow marrow no longer produces blood, although in the event of severe or chronic anemia, it can transform back into red marrow In adults, red marrow is limited to the axial skeleton, pectoral girdle, pelvic girdle, and proximal heads of the humerus and the femur.

60 Bone Development Osteogenesis (a.k.a. ossification) is the process of bone tissue formation. In embryos this leads to the formation of the bony skeleton. In children and young adults, ossification occurs as part of bone growth. In adults, it occurs as part of bone remodeling and bone repair.

61 Formation of the Bony SkeletonBefore week 8, the human embryonic skeleton is made of fibrous membranes and hyaline cartilage. After week 8, bone tissue begins to replace the fibrous membranes and hyaline cartilage. The development of bone from a fibrous membrane is called intramembranous ossification. Why? The replacement of hyaline cartilage with bone is known as endochondral ossification. Why?

62 Growth in Bone Length Epiphyseal cartilage (close to the epiphysis) of the epiphyseal plate divides to create more cartilage, while the diaphyseal cartilage (close to the diaphysis) of the epiphyseal plate is transformed into bone. This increases the length of the shaft.

63 At puberty, growth in bone length is increased dramatically by the combined activities of growth hormone, thyroid hormone, and the sex hormones. As a result osteoblasts begin producing bone faster than the rate of epiphyseal cartilage expansion. Thus the bone grows while the epiphyseal plate gets narrower and narrower and ultimately disappears. A remnant (epiphyseal line) is visible on X-rays (do you see them in the adjacent femur, tibia, and fibula?)

64 Growth in Bone ThicknessOsteoblasts beneath the periosteum secrete bone matrix on the external surface of the bone. This obviously makes the bone thicker. At the same time, osteoclasts on the endosteum break down bone and thus widen the medullary cavity. This results in an increase in shaft diameter even though the actual amount of bone in the shaft is relatively unchanged.

65 Fractures Despite its mineral strength, bone may crack or even break if subjected to extreme loads, sudden impacts, or stresses from unusual directions. The damage produced constitutes a fracture. The proper healing of a fracture depends on whether or not, the blood supply and cellular components of the periosteum and endosteum survive.

66 Fracture Types Open (compound)  bone ends penetrate the skin.Fractures are often classified according to the position of the bone ends after the break: Open (compound)  bone ends penetrate the skin. Closed (simple)  bone ends don’t penetrate the skin. Comminuted  bone fragments into 3 or more pieces Common in the elderly (brittle bones). Greenstick  bone breaks incompletely. One side bent, one side broken. Common in children whose bone contains more collagen and are less mineralized. Spiral  ragged break caused by excessive twisting forces. Sports injury/Injury of abuse. Impacted  one bone fragment is driven into the medullary space or spongy bone of another.

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68 Bone Remodeling Bone is a dynamic tissue.What does that mean? Wolff’s law holds that bone will grow or remodel in response to the forces or demands placed on it. Examine this with the bone on the left.

69 Check out the mechanism of remodeling on the right!Why might you suspect someone whose been a powerlifter for 15 years to have heavy, massive bones, especially at the point of muscle insertion? Astronauts tend to experience bone atrophy after they’re in space for an extended period of time. Why?

70 Nutritional Effects on BoneNormal bone growth/maintenance cannot occur w/o sufficient dietary intake of calcium and phosphate salts. Calcium and phosphate are not absorbed in the intestine unless the hormone calcitriol is present. Calcitriol synthesis is dependent on the availability of the steroid cholecalciferol (a.k.a. Vitamin D) which may be synthesized in the skin or obtained from the diet. Vitamins C, A, K, and B12 are all necessary for bone growth as well.

71 Hormonal Effects on BoneGrowth hormone, produced by the pituitary gland, and thyroxine, produced by the thyroid gland, stimulate bone growth. GH stimulates protein synthesis and cell growth throughout the body. Thyroxine stimulates cell metabolism and increases the rate of osteoblast activity. In proper balance, these hormones maintain normal activity of the epiphyseal plate (what would you consider normal activity?) until roughly the time of puberty.

72 Hormonal Effects on BoneAt puberty, the rising levels of sex hormones (estrogens in females and androgens in males) cause osteoblasts to produce bone faster than the epiphyseal cartilage can divide. This causes the characteristic growth spurt as well as the ultimate closure of the epiphyseal plate. Estrogens cause faster closure of the epiphyseal growth plate than do androgens. Estrogen also acts to stimulate osteoblast activity.

73 Parathyroid Hormone Released by the cells of the parathyroid gland in response to low blood [Ca2+].Causes blood [Ca2+] to increase. PTH will bind to osteoblasts and this will cause 2 things to occur: The osteoblasts will decrease their activity and they will release a chemical known as osteoclast-stimulating factor. Osteoclast-stimulating factor will increase osteoclast activity. PTH increases calcitriol synthesis which increases Ca2+ absorption in the small intestine. PTH decreases urinary Ca2+ excretion and increases urinary phosphate excretion.

74 Decreased Blood [Ca2+] Increased PTH release by parathyroid gland Binds to osteoblast causing decreased osteoblast activity and release of osteoclast-stimulating factor Increased calcitriol synthesis Decreased Ca2+ excretion Increased intestinal Ca2+ absorption OSF causes increased osteoclast activity Decreased bone deposition and increased bone resorption Increased Blood [Ca2+]

75 Clinical Conditions OsteomyelitisOsteo=bone + myelo=marrow + itis=inflammation. Inflammation of bone and bone marrow caused by pus-forming bacteria that enter the body via a wound (e.g., compound fracture) or migrate from a nearby infection. Fatal before the advent of antibiotics.

76 Clinical Conditions OsteoporosisGroup of diseases in which bone resorption occurs at a faster rate than bone deposition. Bone mass drops and bones become increasingly porous. Compression fractures of the vertebrae and fractures of the femur are common. Often seen in postmenopausal women because they experience a rapid decline in estrogen secretion; estrogen stimulates osteoblast and inhibits osteoclast activity. Based on the above, what preventative measures might you suggest?