1. Skeletal System
Chapter 7

2. The Skeleton Support Storage Strength
Attachment scaffold for tendons, ligaments and muscle
Blood cell production

3. Types of Bone
Long Bones – long, as in the arm (radius, ulna, humerus) and thigh (femur)
Short Bones – cube-like, as in wrists (carpal) and ankles (tarsal)
Flat Bones – plate-like, as in ribs, scapulae, some skull bones (parietal)
Irregular Bones – vertebrae, facial bones
Round or Sesamoid Bones – small, round, reside in tendons and next to joints – Knee cap or patella is an example

4. Long Bones

5. Short Bones

6. Flat Bones

7. Irregular Bones

8. Sesamoid Bones

10. Parts of a Long Bone

11. Parts of a Long Bone
Epiphysis – wider, thicker region at the ends of long bones. This usually forms a joint (articulates) with another bone. Mostly made of spongy bone
Diaphysis – the long bone shaft between two epiphyses
Periosteum – the tough, vascular, fibrous covering that is firmly attached to bone and continues into tendons and ligaments. Helps form and repair bone.

12. Parts of a Long Bone Spongy Bone (cancellous bone)
mostly found in the epiphyses
Composed of loosely packed bone matrix with gaps arranged in branching bony plates called trabeculae.
Spongy bone is surrounded by a thin layer of compact bone.

13. Parts of a Long Bone Compact Bone
found in the wall of the bone, especially in the diaphysis
Exists as a rigid long tube with a hollow called the medullary cavity that is surrounded by a thin layer of spongy bone
The thin layer of spongy bone is further lined with a thin membrane called endosteum, which contains bone-forming cells
The medullary cavity lined by the endosteum is filled with soft connective tissue called marrow (usually yellow; red marrow is usually found in spongy bone)
densely packed matrix, having no gaps

14. Red vs. Yellow Marrow
Red blood cells, platelets and most white blood cells form in red marrow; some white blood cells develop in yellow marrow. The color of yellow marrow is due to the much higher number of adipocytes. Both types of bone marrow contain numerous blood vessels and capillaries.
At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type. Adults have on average about 2.6 kg of bone marrow, with about half of it being red.
Red marrow is found mainly in the flat bones such as hip bone , breast bone, skull, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the proximal ends (epiphysis) of the long bones such as femur and humerus.
Yellow marrow is found in the hollow interior of the middle portion of long bones (diaphysis).

15. A Journey into Compact Bone
(Haversian System)

16. Inside an Osteon
(Haversian System)
(Volkman’s canal)

17. Bone Development and Growth
The skeletal system begins to develop in the first few weeks of gestation
Bones develop from connective tissue such as cartilage. They can form in two ways:
Bone can develop in sheet-like layers of connective tissue. These types of bone are called Intramembranous bone.
Bone can also develop from hyaline cartilage. These bones are called Endochondral bone.

18. Intramembranous Ossification
Unspecialized (primordial or primitive) connective tissue cells form membrane-like layers at sites of future bones
These primordial cells are supplied with O2 and nutrition through a dense network of blood vessels and the primordial cells actually form layers around the blood vessels
The primordial cells grow large and specialize into osteoblasts (bone-forming cells)
Osteoblasts secrete bone matrix around themselves, creating spongy bone along the blood vessels
Further along in development some spongy bone can become more dense and form compact bone

20. Endochondral Ossification
Most bones of the human skeleton are endochondral bones
Hyaline cartilage is what exists in the place of endochondral bone early in development
Chondrocytes reside in lacunae and keep growing – their lacunae grow as well
The matrix of the cartilage begins to disintegrate and the chondrocytes die
As cartilage decomposes, a periosteum develops all round
Blood vessels and primordial connective tissue cells invade the decomposing sites
Invading primordial cells differentiate into osteoblasts and start forming spongy bone in place of the cartilage (just like intramembranous bone formation)
Once the osteoblasts are completely trapped in their bony matrix, they are called osteocytes
Osteoblasts from the periosteum deposit compact bone around the spongy bone forming in the diaphysis – this thickens the bone

21. Endochondral Ossification, cont’d.
In long bones endochondral ossification begins in the middle of the diaphysis – this is called the primary ossification center
The epiphyses remain cartilaginous and continue to grow
Eventually, spongy bone forms from the cartilage in the epiphyses – this is called the secondary ossification center
The primary ossification center (diaphysis) and the secondary ossification centers (epiphyses) are separated from each other by a band of cartilage called the Epiphyseal plate

22. Growth at the Epiphyseal Plates
The chondrocytes in this plate are arranged in 4 layers
The first layer - layer closest to the end of the epiphyses contain resting chondrocytes – they do not actively grow. This layer also attaches the epiphyseal plate to the spongy bone tissue of the epiphysis
The second layer contains chondrocytes dividing mitotically. As they divide and form cartilaginous matrix around them, the epiphyseal plate thickens
As the cells divide, the older chondrocytes enlarge and thicken the plate even more – this forms the third layer
This activity lengthens the bone
Osteoblasts invade the growing plate and deposit a calcified matrix around the older cells. The old cartilage cells die.
The fourth layer is basically made up of dead chondrocytes trapped in a calcium matrix

23. Layers of the Epiphyseal Plate
(1st Layer – resting chondrocytes)
(2nd Layer – chondrocyte mitosis)
(3rd Layer- chondrocytes enlarging)
(4th Layer)
Layers of the Epiphyseal Plate
Spongy bone and red marrow

24. Growth at the Epiphyseal Plates, cont’d.
Eventually, the fourth layer of the epiphyseal plate is invaded by cells called osteoclasts, which are large, multinucleated cells that are created from the fusion of white blood cells called monocytes
Osteoclasts dissolve the calcified matrix with lysosomes and phagocytize it
That allows bone-forming osteoblasts to invade the area and deposit bone matrix
Osteoclasts also invade the center of the diaphysis and dissolve some of the matrix. This forms the medullary cavity

25. Growth Arrest
The growth and ossification of the diaphysis and the epiphysis continues until the two ossification centers meet.
Once the sites meet, bone growth is no longer possible in that area
Some hyaline cartilage remains at the end of epiphyses as articular cartilage
Children have epiphyseal plates in their bones – indicating the possibility of further growth

32. Hydroxyapatite (a type of calcium phosphate)

33. 33% Organic (protein)
components
67% inorganic
components

34. Bone Growth and Repair
Balanced nutrition, adequate exposure to sunlight, hormones and exercise all contribute to bone growth and repair
Calcium and phosphate salts
Vitamin D3 (Cholecalciferol) – helps in calcium absorption and is found in eggs, milk and foods fortified with it
Vitamin A is needed for osteoblast and osteoclast activity
Vitamin C is needed for collagen development, so a lack of it will inhibit bone development
Vitamin K and B12 are needed for protein synthesis in bones

35. Bone Growth and Repair
Growth hormone from the pituitary gland in the brain stimulates division of chondrocytes in epiphyseal plates
Lack of it will cause pituitary dwarfism
Too much will cause pituitary gigantism
Some adults acquire an excess of growth hormone and develop an exaggerated growth of certain body parts like the jaw and hands – this is called acromegaly
Male and female hormones (estrogen and testosterone) becomes active at puberty and promote bone growth
Physical exercise stimulates bone growth – this is called hypertrophy and lack of exercise causes bone loss – called atrophy

36. Calcium Resorption and Deposition
All through life, osteoclasts reabsorb bone and octeoblasts replace bone
When blood calcium levels are low, parathyroid hormone stimulates osteoclasts to break down bone tissue, releasing calcium from bone matrix into blood
When there is too much calcium in the blood, the thyroid gland releases calcitonin which stimulates osteoblasts to pick up calcium from blood and store it in bone matrix – thus forming new bone tissue
Too much calcium in the blood also inhibits osteoclast activity

38. Bone and Joint Pathology
Rheumatoid arthritis - autoimmune disease, affects smaller joints (e.g., hands)
Osteosarcoma - malignant bone tumor
Osteoporosis - porous bones
Gout - deposition of sodium urate crystals
Osteoarthritis - wear and tear arthritis, major joints (e.g., knees)

39. Arthritis
The most common form of arthritis, osteoarthritis is also known as degenerative joint disease and occurs following trauma to the joint, following an infection of the joint or simply as a result of aging. There is emerging evidence that abnormal anatomy may contribute to early development of osteoarthritis.

40. Osteogenesis Imperfecta
Osteogenesis imperfecta (OI) literally means imperfectly formed bones. People with OI have an error (mutation) in the genetic instructions on how to make strong bones. As a result, their bones break easily.
One of the genes that tells the body how to make a specific protein (type I collagen) is defective in people with OI. Type I collagen is a major component of the connective tissues in bones, ligaments, teeth, and the white outer tissue of the eyeballs (sclera). As a result of the defect, the body may not produce enough type I collagen or it may produce poor quality collagen. The result in both cases is the same: fragile bones that break easily. However, the bones heal at a normal rate.

41. Osteogenesis Imperfecta

42. Osteoporosis
Osteoporosis is a term that means "porous bones." It is a skeletal disease affecting women and men. Osteoporosis is a condition in which bones have lost minerals—especially calcium—making them weaker, more brittle, and susceptible to fractures (broken bones). Any bone in the body can be affected by osteoporosis, but the most common places where fractures occur are the back (spine), hips, and wrists.
Women are 4 times as likely than men to develop it – usually after menopause

43. Bone Movement

44. More Joints

46. Fractures

50. BONES OF THE SKULL

51. How many bones? There are 22 bones in the skull
8 bones form the cranium
14 bones make up the face
21 of the 22 bones are immobile and interlocking
The 22nd, is the mandible (a facial bone) - the only movable bone

52. Cranial Bones - 8 The cranium protects the brain
1 Frontal bone – contains frontal sinuse
2 Parietal bones (held together by the sagittal suture)
1 Occipital bone (Back of skull and base of cranium)
2 Temporal bones
1 Sphenoid bone – contains spenoid sinuses, sella turcica, optic canal, foramen ovale, foramen rotundum and foramen spinosum
1 Ethmoid bone – contains superior nasal conchae, middle nasal conchae, perpendicular plate, crista galli, cribiform plate, ethmoid sinuses, olfactory foramina

53. Facial Bones
2 Maxillary bones (upper jaw) – contains maxillary sinuses
2 Palatine bones
2 Zygomatic bones
2 Lacrimal bones
2 Nasal bones
1 Vomer
2 Inferior nasal conchae
1 Mandible – contains mental foramen, ramus, coronoid process, alveolar arch, mandibular foramen

54. Sinuses Cavities in bones
2 Frontal sinuses (Cranium)
2 Sphenoid sinuses (Cranium)
2 groups of Ethmoid sinuses (Cranium)
2 Maxillary sinuses (Face)

59. Foramina of Skull 1. Anterior Palatine Foramen
2. Palatine Process of Maxilla
3. Palatine
4. Greater Palatine Foramen
5. Lesser Palatine Foramen
6. Pterygoid Processes of Sphenoid
7. Zygomatic Process
8. Squamous Part of Temporal Bone
9. Mandibular Fossa
10. Styloid Process
11. Stylomastoid Foramen
12. Mastoid Process
13. Mastoid Foramen
14. Superior Nuchal Line
15. External Occipital Protruberance
16. Median Nuchal Line
17. Inferior Nuchal Line
18. Foramen Magnum
19. Condyloid Canal
20. Occipital Condyle
21. Hypoglossal Canal
22. Jugular Foramen
23. Carotid Canal
24. Foramen Spinosum
25. Foramen Ovale
26. Foramen Lacerum
27. Vomer
28. Transverse Palatine Suture
29. Median Palatine Suture

60. Infantile Skull
Not completely developed at birth – leaves room for growth and molding
Fibrous membranes called Fontanels connect cranial bones
Anterior fontanel-closes last (by end of year 2)
Posterior fontanel – closes in month 2 after birth
Sphenoid fontanel – closes in 3 months after birth
Mastoid fontanel – closes at the end of the 1st year

61. The Vertebral Column

62. The Vertebral Column Extends from skull to pelvis
Made of bone called vertebrae that are separated by discs of fibrocartilage
Provides support as well as movement
An adult has 26 bones in the column
7 cervical
12 thoracic
5 lumbar
sacral (These are 5 fused vertebrae and counted as 1)
coccyx region (These are 4 fused vertebrae and counted as 1)

63. Convex anteriorly
Concave anteriorly
Convex anteriorly
(PELVIC)
Concave anteriorly

64. Curvatures
A normal column has four curvatures which offer strength and resiliency
Cervical curvature –secondary - develops when baby learns to hold head up
Thoracic curvature
Lumbar curvature – secondary - develops when child learns to stand up
Pelvic curvature

65. Abnormal Curvatures Kyphosis – Exaggerated thoracic curvature
Lordosis – Exaggerated lumbar curvature
Scoliosis - lateral bending of the vertebral column

66. Kyphosis and Lordosis This condition is also called roundback
This condition is also called swayback

67. Scoliosis – Abnormal Curvature
Congenital scoliosis is caused by defects in the spine present at birth. This form of scoliosis is also accompanied by other disorders of various organs.
Neuromuscular scoliosis is caused by problems with the nerves or muscles. They are unable to support the spine in its normal position. The most common causes of this type of scoliosis are cerebral palsy (see cerebral palsy entry) and muscular dystrophy (see muscular dystrophy entry).
Degenerative scoliosis is caused by deterioration of the bony material (discs) that separate the vertebrae. Arthritis in the spinal cord can also lead to degenerative scoliosis.
In four out of five scoliosis cases, however, the cause is unknown. Such cases are known as idiopathic scoliosis. Children with idiopathic scoliosis have not suffered from related disorders such as bone or joint disease early in life. Some researchers believe that the condition may be inherited, but scientists have yet to find a gene responsible for the disease.

68. Vertebrae A single bone of the vertebral column is called a vertebra.
A typical vertebra is made up of a drum-like part called the body – a longitudinal row of these bodies support the head and trunk.
There are intervertebral discs between the rough surfaces of the bodies
Adjacent bodies are joined by two types of ligaments, one on the anterior side and one on the posterior side
The anterior longitudinal ligaments
The posterior longitudinal ligaments

70. Vertebral Ligaments 1. Anterior longitudinal ligament
2. Posterior longitudinal ligament

71. Cervical Vertebrae
These seven bones are the smallest of the vertebrae that comprise the neck and support the head.
The first vertebra is the atlas, which appears as a bony ring and supports the head.
The second vertebra is the axis, with its toothlike dens that pivots within the atlas.
Features that separate cervical vertebrae from the rest are the bifid spinous processes and transverse foramina.

73. Notice how the dens of the
Axis pivots inside the atlas.

74. The Shape of the rest of the Cervical Vertebrae
Cervical vertebrae have the smallest bodies of all vertebrae

75. Spina Bifida
Often called open spine, spina bifida affects the backbone and, sometimes, the spinal cord. It is among the most common severe birth defects in the United States, affecting 1,500 to 2,000 babies (one in every 2,000 live births)
Spina Bifida means cleft spine, which is an incomplete closure in the spinal column.

76. Spina Bifida

77. Thoracic Vertebrae

78. Thoracic Vertebrae Twelve thoracic vertebrae articulate with the ribs.
These bones are larger and stronger than the cervical vertebrae.

79. Lumbar Vertebrae
The five massive lumbar vertebrae support the weight of the body. They have the largest bodies of all vertebrae
Body

80. Sacrum and Coccyx

81. Sacrum, Coccyx Sacrum Coccyx
The sacrum is a triangular structure at the base of the vertebral column made up of five vertebrae fused into one bone.
The spinous processes of these vertebrae fuse to form a ridge of tubercles that have dorsal sacral foramina along their sides.
On the ventral surface of the sacrum, four pairs of pelvic sacral foramina provide passageways for nerves and blood vessels.
Coccyx
The coccyx is the lowermost portion of the vertebral column and is composed of four fused vertebrae.

82. Thoracic Cage

83. The Thoracic Cage
The thoracic cage includes the ribs, thoracic vertebrae, sternum, and costal cartilages.
It supports the pectoral girdle and upper limbs, functions in breathing, and protects thoracic and upper abdominal organs.
Ribs
Normally, there are 12 pairs of ribs that attach to the thoracic vertebrae.
The first seven pairs of ribs are true (or vertebrosternal) ribs that join the sternum directly by their costal cartilages.
The remaining five pairs are false ribs: the first three pairs are vertebrochondral ribs, and the last two pairs are floating ribs.
Features of a typical rib include a shaft, costal groove, anterior (sternal) end, head, neck, and tubercle.
The head articulates with the vertebrae; the tubercle articulates with the transverse process of the thoracic vertebrae.
Sternum
The sternum (breastbone) is located along the anterior midline of the thoracic cage.
It consists of an upper manubrium, middle body, and lower xiphoid process.

84. Ribs Spinous Process Articular facet Lamina Neck of rib Pedicle Body
Shaft
Articular facet
Lamina
Neck of rib
Pedicle
Body
Facet
Vertebral Foramen
Anterior (sternal) end of rib

85. Pectoral Girdle
Made up of four parts:
2 clavicles and
2 scapulae

86. Scapula Superior border Lateral border Medial border
The scapulae are flat, triangular bones on either side of the upper back.
A spine divides the scapula into unequal portions.
The spine leads to the acromion process (articulates with clavicle) and coracoid process (provides attachments for limb and chest muscles).
The glenoid cavity articulates with the head of the humerus.

87. Clavicle
S-shaped
Medial (Sternal) side articulates with upper side of manubrium
Lateral side (acromial) meets the acromion of the scapulae
Help hold shoulders in place
Break easily due to the elongated S shape

88. Upper Limbs Humerus Radius Ulna Hand and wrist
Extends from scapula to elbow
The “head” fits into the glenoid cavity of scapula
It articulates with the scapulae at its head, with the radius at the capitulum, and with the ulna at the trochlea.
Radius
Located on thumb side of the forearm
Partners up with a slightly longer bone – the ulna
Extends from elbow to wrist and crosses over the ulna
Ulna
On the proximal end (elbow end) it has a wrench-like opening called the trochlear (semilunar) notch which articulates with the trochlea of the humerus
The olecranon process lies above the trochlear notch and the coronoid process lies below the trochlear notch - these help with movement of upper arm at the elbow
At the distal end, the “head” articulates with the ulnar nothch of the radius and also is separated by a cartilaginous disc from the triquetrum one of the carpals (wrist)
Hand and wrist
The wrist of the hand is made up of eight carpal bones bound into a carpus.
The framework of the hand is made up of five metacarpal bones.
The fingers are composed of three phalanges in each finger except the thumb, which lacks the middle phalanx.

89. Humerus

90. Radius and Ulna

91. Hand and Wrist

92. Pelvic Girdle
The pelvic girdle consists of the two coxal bones and the sacrum; it supports the trunk of the body on the lower limbs.
The pelvic girdle supports and protects the lower abdominal and pelvic organs.
Each Coxal bone is made up of three bones: iilium, ischium, and pubis, that are fused in the region of the acetabulum, the cuplike depression that articulates with the head of the femur.
The ilium is the largest and most superior portion of the coxal bone and joins the sacrum at the sacroiliac joint.
Features of the ilium include the iliac crest, and anterior superior iliac spine.
The ischium forms the L-shaped portion that supports weight during sitting.
Fractures of the ischium include the ischial tuberosity and ischial spine.
The pubis comprises the anterior portion of the coxal bones and articulates at the symphysis pubis which has fibrocartilage.
The large opening, the Obturator Foramen lies within each pubis.
The greater pelvis is above the pelvic brim and the lesser pelvis is below it.
There are structural differences between males and female pelves

93. Pelvic Girdle

94. Pelvic Girdle – Male vs. Female
(Fibrocartilage)
Male

95. The Coxa

96. The Lower Limb
Femur
The femur, or thighbone, extends from the hip to the knee and is the longest bone in the body.
Its head articulates with the acetabulum; it articulates with the tibia at the medial and lateral condyles.
Other features of the femur include the fovea capitis, neck, and greater and lesser trochanters.
The patella (kneecap) is located in the tendon that passes over the knee.
Tibia
The tibia (shinbone) supports the weight of the body and articulates with the femur (medial and lateral condyles) and with the tarsal bones of the foot.
Its anterior tibial tuberosity is the point of attachment for the patellar ligament.
Other features of the tibia include the medial malleolus (inner ankle).
Fibula
The fibula is a slender bone lying lateral to the tibia; it does not bear body weight.
The lateral malleolus forms the lateral ankle.
Foot and ankle

97. Femur
Articulates with acetabulum of coxal bone

98. Fibula and Tibia (Shinbone) (Lies lateral to tibia)
(The medial malleolus forms the lateral ankle.)
(The lateral malleolus forms the lateral ankle.)

99. Foot and Ankle
The ankle is composed of seven tarsal bones, forming a tarsus.
The talus articulates with the tibia and fibula.
The calcaneus supports the body weight.
The instep of the foot consists of five metatarsal bones and provides an arch.
Each toe is made up of three phalanges, with the exception of the great toe, which lacks a middle phalanx.

100. Foot and Ankle
The talus articulates with the tibia and fibula.

101. Foot and Ankle

102. 3 Types of Levers Force Resistance Pivot Force Resistance Pivot

103. Lever in the Body
The straightening of the upper limb at the elbow – First class lever ( force-pivot-resistance)
The mandible being lowered and raised within the temporal bone - Second class lever (force-resistance-pivot)
Bending of the arm at the elbow – Third-class lever (resistance-force-pivot)

104. THE END