1. The Human Skeleton

2. Divisions of the Skeleton
Axial skeleton – skull, vertebrae, and bony thorax
Appendicular skeleton – bones of the arms and legs, including their associated girdles

3. The Skull
Consists of 22 bones interlocked along sutures (all except the mandible)
8 bones make up the cranium
13 bones make up the facial skeleton
Mandible = lower jawbone; only movable bone held to the cranium by ligaments
Orbit of the eye is formed by cranial and facial bones

4. The Cranium Encloses and protects the brain
Surface provides attachments for muscles involved in chewing and head movements

5. Sinuses Air-filled cavities of the cranium Lined with mucous membranes
All connected by passageways to the nasal cavity
Function to reduce the weight of the skull and increase voice intensity and resonance

6. Cranial Bones Frontal bone Parietal bones (2) Occipital bone
Temporal bones (2)
Sphenoid bone
Ethmoid bone

7. Frontal Bone Features Supraorbital foramen Frontal sinuses
Develops in 2 parts that grow together by 5-6 years old

8. Parietal Bone Features
Sagittal suture
Coronal suture

9. Occipital Bone Features
Lambdoidal suture
Foramen magnum
Occipital condyles

11. Temporal Bone Features
Squamosal suture – temporal to parietal
External auditory meatus
Mandibular fossae – joint with mandible
Mastoid process – neck muscle attachment
Styloid process – below EAM, anchors muscles of tongue and pharynx
Zygomatic process – helps form cheek prominence

12. Sphenoid Bone Features
Wedged between several other bones in anterior portion of the cranium
2 winglike structures extend laterally toward each side of the skull
Sella turcica – houses pituitary gland
Sphenoidal sinuses

13. Ethmoid Bone Features Located in front of the sphenoid bone
Consists of 2 masses on each side of the nasal cavity
Cribriform plates – join the 2 parts of the ethmoid bone
Perpendicular plate – form most of nasal septum
Superior and middle nasal conchae – support mucous membranes of the nose
Ethmoid sinuses
Crista galli – triangular process that projects upward from the cribriform plates; place of attachment for membranes around the brain

15. Facial Skeleton 13 immovable bones + the mandible
Provides attachments for muscles for facial expressions and jaw movements

16. Bones of the Facial Skeleton
Maxillary bones (2)
Palatine bones (2)
Zygomatic bones (2)
Lacrimal bones (2)
Nasal bones (2)
Vomer bone
Inferior nasal conchae (2)
Mandible

17. Maxillary Bone Features
Form upper jaw
All other immovable facial bones articulate with them
Hard palate
Sockets of upper teeth
Maxillary sinuses
Palatine processes – where the maxillary bones meet

18. Palatine Bone Features
L-shaped bones behind the maxillae
Posterior hard palate

19. Zygomatic Bone Processes
Prominences of the cheeks
Temporal processes

20. Lacrimal Bone Features
Thin, scalelike bones between the ethmoid bone and maxillae in the medial walls of the orbits
Groove in anterior portion provides pathway for tears to the nasal cavity

21. Nasal Bone Features
Form the bridge of the nose

22. Vomer Bone Features
Joins perpendicular plate of ethmoid bone to form the nasal septum

23. Inferior Nasal Conchae Features
Scroll-shaped bones attached to lateral walls of the nasal cavity
Support mucous membranes of the nose

24. Mandible Features Ramus – attachment for large chewing muscles
Mandibular condyle – articulates with mandibular fossae of temporal bones
Alveolar border – houses lower tooth sockets
Mandibular foramen – carries nerves and blood vessels to the lower teeth; dental injection site
Mental foramen – carries branches of nerves and blood vessels of the mandibular foramen

25. Review of Fontanels
Fontanels = membranous areas where the skull is incompletely developed; soft spots
Permit some movement during childbirth
Eventually close as bones grow together
Posterior fontanel – closes at 2 months
Sphenoid fontanel – closes at 3 months
Mastoid fontanel – closes near end of 1st year
Anterior fontanel – closes near end of 2nd year

26. Other Infantile Skull Features
Relatively small face
Prominent forehead
Large orbits
Small jaw
Small nasal cavity
Sinuses are incompletely formed
Frontal bone is in 2 parts
Thin skull bones, but not easily fractured

27. The Vertebral Column Extends from the skull to the pelvis
Forms the vertical axis of the skeleton
Composed of vertebrae, intervertebral disks, and ligaments

28. Functions of the Vertebral Column
Supports the head and trunk
Permits movement
Protects the spinal cord which passes through the vertebral canal

29. Development of the Vertebral Column
Consists of 33 bones at infancy
5 fuse to form the sacrum
4 fuse to form the coccyx
26 bones are found in the adult vertebral column

30. Curvatures of the Vertebral Column
Primary curvatures are anteriorly concave
Thoracic curvature
Pelvic curvature
Secondary curvatures are anteriorly convex
Cervical curvature
Lumbar curvature
Cervical curvature develops when a baby begins to hold up its head
Lumbar curvature develops when a child begins to stand

31. Typical Vertebra Body – thick, drum-shaped, anterior portion of bone
Intervertebral disks – cushion and soften forces caused by movements
Pedicles – 2 short stalks that project posteriorly from each vertebral body
Laminae – 2 plates that arise from pedicles to fuse and form the spinous process
Transverse processes – between the pedicles and laminae; project laterally and posteriorly

32. Typical Vertebra continued…
Vertebral arch – formed by the pedicles, laminae, and spinous process; around the vertebral foramen
Vertebral foramen – opening through which the spinal cord passes
Intervertebral foramina – passageways for spinal nerves; between adjacent vertebrae

33. Cervical Vertebrae 7 vertebrae Make up the neck region
Smallest vertebrae
Denser bone tissues than the other regions
Distinctive because they have transverse foramina (passageways for arteries leading to the brain)
Spinous processes are uniquely forked (C2-C6)
C7 = vertebrae prominens; spinous process is longer and protrudes beyond the other cervical vertebrae

34. Atlas C1 Supports the head Has no body or spine
Consists of a bony ring with 2 transverse processes
Facets – kidney-shaped areas on the superior surface that articulate with the occipital condyles

35. Axis C2
Dens – toothlike process that projects upward and lies in the ring of the atlas
As the head is turned from side to side, the atlas pivots around the dens.

36. Thoracic Vertebrae 12 in number Larger than cervical vertebrae
Long, pointed spinous process which slopes downward
Facets on sides of vertebral body articulate with the ribs
Bodies of the vertebrae increase in size from T3 down  can bear an increasing load of body weight

37. Lumbar Vertebrae 5 in number Located in the small of the back
Larger, stronger, and support more weight than the others
Transverse processes project posteriorly at sharp angles
Short, thick spinous processes are nearly horizontal

38. Sacrum Triangular structure at the base of the vertebral column
5 vertebrae fuse to form the sacrum between years of age
Fused spinous processes form a ridge of tubercles called the median sacral crest
Dorsal sacral foramina – openings to the sides of the tubercles through which nerves and blood vessels pass
Sacral canal – formed from vertebral foramina and opens at the sacral hiatus

39. Coccyx Tailbone Lowest part of the vertebral column
Made of 4 vertebrae that fuse by the 25th year
Acts as a shock absorber when sitting

40. Vertebral Column Disorders
Ruptured/herniated disk – outer layers of the intervertebral disk are broken and the central mass of the disk is squeezed out from extra pressure, pressing on the spinal cord and spinal nerves  pain, numbness, loss of muscular function

41. Curvature Disorders of the Spine
Kyphosis – hunchback; exaggerated thoracic curvature
Scoliosis – abnormal lateral curvature
Lordosis – swayback; exaggerated lumbar curvature

42. Thoracic Cage
Includes ribs, thoracic vertebrae, sternum, and costal cartilages
Supports the shoulder girdle and upper limbs
Protects viscera
Plays a role in breathing

43. Ribs 12 pair – one pair for each vertebra
True ribs – 1st 7 rib pairs; join the sternum directly by costal cartilages
False ribs – bottom 5 rib pairs; do not join the sternum directly
Cartilages of the upper 3 false ribs join the cartilage of the 7th rib
Floating ribs – last 2 rib pairs; no attachment to the sternum

44. Rib Structure
Long, slender shaft which curves around the chest and slopes downward
Head – enlarged area on posterior end that articulates with own vertebra and next higher vertebra
Tubercle – small knoblike process that articulates with transverse process of vertebra
Costal cartilages – hyaline cartilage

45. Sternum Breastbone Develops in 3 parts:
Manubrium – articulates with clavicles at clavicular notches
Body – fuses to manubrium at middle age at the sternal angle
Xiphoid process – begins as cartilage, slowly ossifies, and fuses to the body at middle age
Red bone marrow in sternum produces RBCs into adulthood

46. Pectoral Girdle Made of 2 clavicles and 2 scapulae
Supports upper limbs
Provides attachment for muscles that move the upper limbs

47. Clavicles Slender, rodlike bones with elongated S shapes
Located at base of the neck and run horizontally between the sternum and the shoulders
Sternal ends – articulate with the manubrium
Acromial ends – articulate with the scapulae
Brace the scapulae, holding the shoulders in place
Structurally weak

48. Scapulae
Broad, triangular bones located on either side of the upper back
Spine – divides posterior surface
Supraspinous fossa – area above the spine
Infraspinous fossa – area below the spine
2 processes at the head:
Acromion process – forms tip of the shoulder and articulates with the clavicle
Coracoid process – curves anteriorly and inferiorly to the clavicle
Glenoid cavity – between the acromion and coracoid processes; articulates with the head of the humerus

49. Upper Limb Bones
Bones form the framework of the arm, forearm, and hand
Bones function as levers for muscle contraction
Includes:
Humerus (2)
Radius (2)
Ulna (2)
Carpals (16)
Metacarpals (10)
Phalanges (28)

50. Humerus Long bone that extends from scapula to the elbow
Head fits into glenoid cavity of scapula
Greater tubercle – on leteral side
Lesser tubercle – on anterior side
Surgical neck – tapering region below head and tubercles (common fracture site)
Deltoid tuberosity – V shaped rough area near the middle of the shaft on the lateral side  attachment for the deltoid muscle

51. Humerus Bone Features continued…
Coronoid fossa – process where the elbow bends: receives the ulna
Capitulum – articulates with the radius
Olecranon fossa – on posterior surface, receives the olecranon process of the ulna when the elbow straightens
Trochlea – articulates with the ulna
Epicondyles – attachments for elbow muscles and ligaments

52. Radius On thumb side of forearm Shorter than the ulna
Extends from the elbow to the wrist and crosses over the ulna when hand is turned over at the wrist
Head is thick and disk-like; articulates with the capitulum of the humerus and radial notch of the ulna
Radial tuberosity – process just below the head; attachment for the biceps
Styloid process – attachment for wrist ligaments at the distal end

53. Ulna Longer than the radius Overlaps end of humerus posteriorly
Trochlear notch – at proximal end, wrench-like opening that articulates with the trochlea of the humerus
Olecranon process – above the trochlear notch; attachment for triceps that straightens the upper limb at the elbow; fits into olecranon fossa
Coronoid process – below trochlear notch, fits into coronoid fossa when elbow bends
Styloid process – at distal end provides attachment for wrist ligaments

55. Wrist Wrist consists of carpals bound in 2 rows of 4 bones each
Articulate with radius and ulna proximally and metacarpals distally
Carpal bones are:
Pisiform
Triquetrum
Lunate
Scaphoid
Hamate
Capitate
Trapezoid
Trapezium

56. Metacarpals Form the palm of the hand 5 per hand
Long bones with rounded distal ends (knuckles)
Articulate with carpals and phalanges
Lateral metacarpal is the most freely moveable
Numbered 1-5, starting at the thumb

57. Phalanges Finger bones 3 per finger (proximal, middle, and distal)
2 in thumb – no middle phalanx

58. Pelvic Girdle Consists of 2 coxae
Coxae articulate with each other anteriorly and the sacrum posteriorly
Pelvis – formed by the sacrum, coccyx, and pelvic girdle
Girdle supports the trunk of the body, provides attachments for lower limb muscles, protects the bladder, distal end of the large intestine, and internal reproductive organs
Body weight is transmitted through the pelvic girdle to the lower limbs

59. Os Coxae Each coxa develops from 3 parts:
Ilium
Ishium
Pubis
Acetabulum – cup-shaped cavity where the 3 parts of coxa fuse

60. Ilium Largest and most superior portion of the coxa
Flares outward and forms the prominence of the hip
Iliac crest – margin of the ilium
Iliac fossa – smooth, concave surface on anterior aspect of the ilium
Sacroiliac joint – where ilium and sacrum join
Anterior superior iliac spine – found lateral to the groin, provides attachments for ligaments and muscles
Posterior superior iliac spine – on posterior border

61. Ischium Forms lowest portion of the coxa L-shaped
Ischial tuberosity – rough surface that points down and back; supports body weight when sitting
Ischial spine – sharp projection above ischial tuberosity, near the junction between the ilium and the ischium
Area between ischial spines is the shortest diameter of the pelvic outlet; felt during vaginal exams

62. Pubis Anterior portion of coxa
Symphysis pubis – fibrocartilage joint between the 2 pubic bones
Pubic arch – angle between pubic bones
Obturator foramen – largest opening in the body
Formed between ischium and pubis
Covered and nearly closed by obturator membrane

63. Male vs. Female Pelvis Male Pelvis: Female Pelvis Heavier bone
More evidence of muscle attachments
Female Pelvis
Iliac bones are more flared
Broader hips
Greater angle of pubic arch
Greater distance between ischial spines and tuberosities
Shorter, flatter sacral curvature
More delicate bones

65. Lower Limb Bones Femur (2) Patella (2) Tibia (2) Fibula (2)
Tarsals (7/foot)
Metatarsals (5/foot)
Phalanges (14/foot)

66. Femur Bone Features Thigh bone Longest bone in body
Extends from hip to knee
Head of femur – large and rounded; projects medially into acetabulum of coxal bone
Fovea capitis – pit on head of femur that marks ligament attachment
Greater trochanter and lesser trochanter – attachments for muscles of buttocks and lower limbs
Linea aspera – longitudinal crest on posterior surface in middle third of shaft
Lateral and medial condyles – articulate with tibia

67. Patella Articulates with the femur on distal anterior surface Kneecap
Flat sesamoid bone located in a tendon that passes anteriorly over the knee
Controls the angle at which the tendon continues toward the tibia  functions in lever actions

68. Tibia Bone Features Shin bone
Larger of 2 leg bones; located on the medial side
Medial and lateral condyles – on proximal end, articulate with condyles of femur
Tibial tuberosity – below condyles on anterior surface; attachment of patellar ligament
Anterior crest – extends downward from tuberosity; site of CT attachments
Medial malleolus – inner ankle
Articulates with fibula and talus on distal end

69. Fibula Bone Features
Long, slender bone located on the lateral side of the tibia
Articulates with the tibia just below the lateral condyle
Lateral malleolus – distal end that forms the outer ankle

70. Bones of the Foot Tarsus – consists of 7 tarsal bones
Talus – tarsal bone that can move freely where it joins the tibia and fibula  ankle
Other tarsals are bound firmly together to support the talus
Calcaneus – largest tarsal bone; heel bone
Located below the talus and projects backward
Helps support weight of the body

71. Metatarsals Numbered 1-5 beginning on the medial side
Ball of the foot formed by the distal ends
Longitudinal arch extends from the heel to the toe; provides a stable, springy base for the body
Transverse arch stretches across the foot
If tissues that bind the metatarsals weaken  fallen arches (flat feet)

72. Phalanges Shorter, but otherwise similar to fingers
3 bones per toe, except 2 in the great toe