2. Learning Objectives:
At the end of the discussion the students must be able to:
Enumerate the major roles of skeletal system
and its parts,
Explain the process of bone formation,
remodelling, repair and aging; and
Acclaim the roles of skeletal system to
human survival.
Jaycris C. Agnes , 2013
3. Topic Outline:
I. Function of Skeletal System
A. Bones
B. Cartilages
C. Tendons and Ligaments
D. Joints
II. General Features of Bone
A. Parts of Bone
B. Bone Cells
D. Bone Surface Markings
E. Bone Ossification, Remodelling and Repair
F. Types of Bones
Jaycris C. Agnes , 2013
4. Topic Outline:
III. General Consideration of Bone Anatomy
A. Division of Human Skeleton
IV. Bone and Calcium Homeostasis
V. Articulation
VI. Effects of Aging on the Skeletal System
Jaycris C. Agnes , 2013
5. Functions of the Skeletal System
Bone
Mechanical
Protection — bones can serve to protect
internal organs, such as the skull protecting
the brain or the ribs protecting
the heart and lungs.
Structure — bones provide a frame to keep
the body supported.
Jaycris C. Agnes , 2013
6. Movement — bones, skeletal
muscles, tendons, ligaments and joints functi
on together to generate and transfer forces
so that individual body parts or the whole
body can be manipulated in three-
dimensional space. The interaction between
bone and muscle is studied in biomechanics.
Sound transduction — bones are important
in the mechanical aspect of
overshadowed hearing.
Jaycris C. Agnes , 2013
7. Synthetic
Blood production — the marrow, located
within the medullary cavity of long bones and
interstices of cancellous bone, produces
blood cells in a process called
hematopoiesis.
Jaycris C. Agnes , 2013
8. Metabolic
Mineral storage — bones act as reserves of
minerals important for the body, most
notably calcium and phosphorus.
Growth factor storage — mineralized bone
matrix stores important growth factors such
as insulin-like growth factors, transforming
growth factor, bone morphogenetic
proteins and others.
Jaycris C. Agnes , 2013
9. Fat storage — the yellow bone marrow acts
as a storage reserve of fatty acids.
Acid-base balance — bone buffers the
blood against excessive pH changes by
absorbing or releasing alkaline salts.
Detoxification — bone tissues can also
store heavy metals and other foreign
elements, removing them from the blood and
reducing their effects on other tissues. These
can later be gradually released for excretion.
Jaycris C. Agnes , 2013
10. Endocrine organ — bone
controls phosphate metabolism by
releasing fibroblast growth factor – 23, which
acts on kidneys to reduce phosphate
reabsorption. Bone cells also release a
hormone called osteocalcin, which
contributes to the regulation of blood
sugar (glucose) and fat deposition.
Osteocalcin increases both
the insulin secretion and sensitivity, in
addition to boosting the number of insulin-
producing cells and reducing stores of fat.
Jaycris C. Agnes , 2013
11. Functions of the Skeletal System
Cartilage
Cartilage provides a model for bone growth
and formation, provides a smooth cushion
between adjacent bones, and provides firm
and flexible support.
Jaycris C. Agnes , 2013
12. Functions of the Skeletal System
Tendons and Ligaments
Tendons attach muscles to bones, and
ligaments attach bones to bones.
Joints
Joints allow movement between bones.
Jaycris C. Agnes , 2013
13. Compact Bone
Compact bone makes up the
outer layer of all bones. Although
it looks dense and solid, It is full
of holes for nerves and blood vessels.
Spongy Bone
Spongy bone contains flat
and needlelike structures
that resist stress. Red bone
marrow may fill the open
spaces in some bones.
Central Cavity
Central cavities in long
bones usually contain
yellow bone marrow (fat).
Outer Membrane
An outer membrane
covers most of a long bone.
The inner portion of a membrane
contains cells that build up and
breakdown bone.
General Features of the Bone
Parts of Bone
Jaycris C. Agnes , 2013
15. General Features of the Bone
Bone Cells
There are several types of cells constituting the
typical bone:
Osteocytes
Mature bone cells
Osteoblasts
Bone-forming cells
Osteoclasts
Bone-destroying cells
Break down bone matrix for remodeling and release
of calcium
Jaycris C. Agnes , 2013
16. Bone Surface Markings
Bones have characteristic surface markings
Structural features adapted for specific functions
There are two major types of surface markings:
1) Depressions and openings
Allow the passage of blood vessels and nerves or form
joints
2) Processes/ Projections
Projections or outgrowths that form joints or serve as
attachment points for ligaments and tendons
Jaycris C. Agnes , 2013
20. Ligament/Tendon Projections
1) Crest: Narrow ridge
of bone (Line: smaller
than a crest)
2) Epicondyle: Raised
area on or above a
condyle
ULNA
Jaycris C. Agnes , 2013
21. 3) Tubercle: Small
rounded projection
4) Tuberosity: large
rounded or
roughened projection
5) Trochanter: very
large, blunt projection
(only on femur)
Proximal Tibia
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25. Depressions
4) Sinus: Cavity within a
bone; filled with air
and lined with
mucous membranes
5) Foramen: Round or
oval opening
Foramen Magnum
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27. Bone Markings
Projections
1) Condyle
2) Head
3) Facet
4) Ramus
5) Crest
6) Epicondyle
7) Tubercle
8) Tuberosity
9) Trochanter
10) Spine
Depressions
1) Meatus
2) Foramen
3) Fossa
4) Fissure
5) Sinus
6) Sulcus or Groove or
Furrow
Jaycris C. Agnes , 2013
28. Bone Ossification
The formation of bone during the fetal stage
of development occurs by two
processes: Intramembranous
Ossification and Endochondral
Ossification.
Jaycris C. Agnes , 2013
29. Intramembranous Ossification
Intramembranous ossification mainly occurs
during formation of the flat bones of
the skull but also the mandible, maxilla, and
clavicles; the bone is formed from
connective tissue such
as mesenchyme tissue rather than from
cartilage.
Jaycris C. Agnes , 2013
30. Intramembranous Ossification
The steps in intramembranous ossification
are:
1. Development of ossification center.
2. Calcification.
3. Formation of trabeculae.
4. Development of periosteum.
Jaycris C. Agnes , 2013
31. Endochondral Ossification
Endochondral ossification, on the other
hand, occurs in long bones and most of the
rest of the bones in the body; it involves an
initial hyaline cartilage that continues to
grow.
Jaycris C. Agnes , 2013
32. Endochondral Ossification
The steps in endochondral ossification
are:
1. Development of cartilage model
2. Growth of cartilage model
3. Development of the primary ossification center
4. Development of the secondary ossification
center
5. Formation of articular cartilage and epiphyseal
plate
Jaycris C. Agnes , 2013
34. Bone Growth
Does drinking milk can make you
taller?
Jaycris C. Agnes , 2013
35. Bone Remodelling
Bone remodelling consists of removal of
existing bone by osteoclasts and deposition
of new bone by osteoblasts.
Jaycris C. Agnes , 2013
37. Types of Bones
Bones can be classified into five types based on
shape:
Long
Short
Flat
Irregular
Sesamoid
Jaycris C. Agnes , 2013
38. Types of Bones
Long Bones
Greater length than width and are slightly curved for strength
Femur, tibia, fibula, humerus, ulna, radius, phalanges
Short bones
Cube-shaped and are nearly equal in length and width
Carpal, tarsal
Flat bones
Thin and composed of two nearly parallel plates of compact bone tissue
enclosing a layer of spongy bone tissue
Cranial, sternum, ribs, scapulae
Irregular bones
Complex shapes and cannot be grouped into any of the previous
categories
Vertebrae, hip bones, some facial bones, calcaneus
Sesamoid bones
Protect tendons from excessive wear and tear
Patellae, foot, hand
Jaycris C. Agnes , 2013
39. General Consideration of Bone Anatomy
The human skeleton consists of 206 named bones
Bones of the skeleton are grouped into two principal
divisions:
Axial skeleton
Consists of the bones that lie around the longitudinal axis of
the human body
Skull bones, auditory ossicles (ear bones), hyoid
bone, ribs, sternum (breastbone), and bones of the vertebral
column
Appendicular skeleton
Consists of the bones of the upper and lower limbs
(extremities), plus the bones forming the girdles that connect
the limbs to the axial skeleton
Jaycris C. Agnes , 2013
43. Skull
Skull (cranium)
Consists of 22 bones
Bones of the skull are grouped into two
categories:
Cranial bones
Eight cranial bones form the cranial cavity
Frontal bone, two parietal bones, two temporal bones, the
occipital bone, the sphenoid bone, ethmoid bone
Facial bones
Fourteen facial bones form the face
Two nasal bones, two maxillae, two zygomatic bones, the
mandible, two lacrimal bones, two palatine bones, two inferior
nasal conchae, vomer
Jaycris C. Agnes , 2013
45. Skull
The cranial and facial bones protect and support
special sense organs and the brain
Besides forming the large cranial cavity, the skull
also forms several smaller cavities
Nasal cavity
Orbits (eye sockets)
Paranasal sinuses
Small cavities which house organs involved in hearing
and equilibrium
Jaycris C. Agnes , 2013
46. Skull
Immovable joints called sutures fuse most of the
skull bones together
The skull provides large areas of attachment for
muscles that move various parts of the head
Skull and facial bones provide attachment for
muscles that produce facial expressions
The facial bones form the framework of the face
and provide support for the entrances to the
digestive and respiratory systems
Jaycris C. Agnes , 2013
47. Skull (Cranial Bones)
Frontal Bone
Forms the forehead
Parietal Bones
Form the sides and roof of the cranial cavity
Temporal Bones
Form the lateral aspects and floor of the cranium
Occipital Bone
Forms the posterior part and most of the base of the cranium
Sphenoid Bone
Lies at the middle part of the base of the skull
Ethmoid Bone
Located on the midline in the anterior part of the cranial floor medial to
the orbits
A major superior supporting structure of the nasal cavity
Contain thin projections called conchae which are lined by mucous
membranes
Increased surface area in the nasal cavity helps to humidify inhaled air
trapping inhaled particles
Jaycris C. Agnes , 2013
51. Skull (Facial Bones)
Nasal Bones
Form the bridge of the nose
Maxillae
Form the upper jawbone
Form most of the hard palate
Separates the nasal cavity from the oral cavity
Zygomatic Bones
commonly called cheekbones, form the prominences of the
cheeks
Lacrimal Bones
Form a part of the medial wall of each orbit
Palatine Bones
Form the posterior portion of the hard palate
Inferior Nasal Conchae
Form a part of the inferior lateral wall of the nasal cavity
Jaycris C. Agnes , 2013
52. Skull (Facial Bones)
Vomer
Forms the inferior portion of the nasal septum
Mandible
Lower jawbone
The largest, strongest facial bone
The only movable skull bone
Nasal Septum
Divides the interior of the nasal cavity into right and left sides
―Broken nose,‖ in most cases, refers to septal damage rather
than the nasal bones themselves
Orbits
Eye socket
Foramina
Openings for blood vessels , nerves , or ligaments of the skull
Jaycris C. Agnes , 2013
59. Skull
Unique Features of the Skull
Sutures, Paranasal sinuses, Fontanels
Sutures
an immovable joint that holds most skull bones together
Paranasal Sinuses
Cavities within cranial and facial bones near the nasal cavity
Secretions produced by the mucous membranes which line the sinuses,
drain into the nasal cavity
Serve as resonating chambers that intensify and prolong sounds
Fontanels
Areas of unossified tissue
At birth, unossified tissue spaces, commonly called ―soft spots‖ link the
cranial bones
Eventually, they are replaced with bone to become sutures
Provide flexibility to the fetal skull, allowing the skull to change shape as
it passes through the birth canal
Jaycris C. Agnes , 2013
62. Auditory Ossicles
The middle ear has 3 tiny bones: the
Malleus, Incus and Stapes.
Stapes is the smallest bone in the body
Helps in hearing.
Jaycris C. Agnes , 2013
65. Hyoid Bone
Does not articulate with
any other bone
Supports the tongue,
providing attachment
sites for some tongue
muscles and for
muscles of the neck and
pharynx
The hyoid bone also
helps to keep the larynx
(voice box) open at all
times
Jaycris C. Agnes , 2013
66. Vertebral Column
Also called the spine, backbone, or spinal
column
Functions to:
Protect the spinal cord
Support the head
Serve as a point of attachment for the ribs, pelvic
girdle, and muscles
The vertebral column is curved to varying
degrees in different locations
Curves increase the column strength
Help maintain balance in the upright position
Absorb shocks during walking, and help protect the
vertebrae from fracture
Jaycris C. Agnes , 2013
68. Vertebral Column
Composed of a series of bones called
vertebrae (Adult=26)
7 cervical are in the neck region
12 thoracic are posterior to the thoracic cavity
5 lumbar support the lower back
1 sacrum consists of five fused sacral
vertebrae
1 coccyx consists of four fused coccygeal
vertebrae
Jaycris C. Agnes , 2013
69. Vertebral Column (Regions)
Cervical Region
Cervical vertebrae (C1–C7)
The atlas (C1) is the first cervical vertebra
The axis (C2) is the second cervical vertebra
Thoracic Region
Thoracic vertebrae (T1–T12)
Articulate with the ribs
Lumbar Region
Lumbar vertebrae (L1–L5)
Provide for the attachment of the large back muscles
Sacrum
The sacrum is a triangular bone formed by the union of five sacral
vertebrae (S1–S5)
Serves as a strong foundation for the pelvic girdle
Coccyx
The coccyx, like the sacrum, is triangular in shape
It is formed by the fusion of usually four coccygeal vertebrae
Jaycris C. Agnes , 2013
77. Thorax
Thoracic cage is formed by the:
Sternum
Ribs
Costal cartilages
Thoracic vertebrae
Functions to:
Enclose and protect the organs in the thoracic
and abdominal cavities
Provide support for the bones of the upper
limbs
Play a role in breathing
Jaycris C. Agnes , 2013
78. Thorax
Sternum
―Breastbone‖ located in the center of the
thoracic wall
Consists of the manubrium, body, xiphoid
process
Ribs
Twelve pairs of ribs give structural support to
the sides of the thoracic cavity
Costal cartilages
Costal cartilages contribute to the elasticity of
the thoracic cage
Jaycris C. Agnes , 2013
82. Appendicular Skeleton
The primary function is movement
It includes bones of the upper and lower
limbs
Girdles attach the limbs to the axial skeleton
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83. Skeleton of the Upper Limb
Each upper limb has 30 bones
The upper limb consists of the bones of the
arm, forearm, wrist, and hand.
Jaycris C. Agnes , 2013
85. Skeleton of the Arm - Humerus
Longest and largest bone of the free part of
the upper limb
The proximal ball-shaped end articulates with
the glenoid cavity of the scapula
The distal end articulates at the elbow with
the radius and ulna
Jaycris C. Agnes , 2013
87. Right humerus in relation to scapula,
ulna, and radius-- Figure 8.5
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88. Jaycris C. Agnes , 2013
Right ulna and radius in relation to the
humerus and carpals -- Figure 8.6
89. Skeleton of the Hand
The carpus (wrist) consists of 8 small bones
(carpals)
Two rows of carpal bones (So Long Top Part, Here
Comes The Thumb)
Proximal row (lateral-medial) - scaphoid, lunate,
triquetrum, pisiform
Distal row (medial-lateral) - hamate ,
capitate,trapezoid, trapezium
Scaphoid - most commonly fractured
Carpal tunnel - space between carpal bones and
flexor retinaculum
Jaycris C. Agnes , 2013
90. Metacarpals and Phalanges
Five metacarpals - numbered I-V, lateral to
medial
14 phalanges - two in the thumb (pollex) and
three in each of the other fingers
Each phalanx has a base, shaft, and head
Joints - carpometacarpal,
metacarpophalangeal, interphalangeal
Jaycris C. Agnes , 2013
91. Right wrist and hand in relation to ulna
and radius -- Figure 8.8
Jaycris C. Agnes , 2013
92. Pectoral Girdle - Clavicle
The clavicle is ―S‖ shaped
The medial end articulates with the
manubrium of the sternum forming the
sternoclavicular joint
The lateral end articulates with the acromion
forming the acromioclavicular joint
Jaycris C. Agnes , 2013
93. The Pectoral (or Shoulder) Girdle
Figure 8.1
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95. Pectoral Girdle - Scapula
Also called the shoulder blade
Triangular in shape
Most notable features include the
spine, acromion, coracoid process and the
glenoid cavity
Jaycris C. Agnes , 2013
98. Skeleton of the Lower Limb
Skeleton of the Lower Limb
Consist of bones of thigh, leg, ankle and foot.
Each lower limb has 30 bones.
Jaycris C. Agnes , 2013
99. Pelvic (Hip) Girdle
Each coxal (hip) bone consists of three bones
that fuse together: ilium, pubis, and ischium
The two coxal bones are joined anteriorly by
the pubic symphysis (fibrocartilage)
Joined posteriorly by the sacrum forming the
sacroiliac joints (Fig 8.9)
Jaycris C. Agnes , 2013
102. Comparing Male and Female Pelves
Males - bone are larger and heavier
Pelvic inlet is smaller and heart shaped
Pubic arch is less the 90°
Female - wider and shallower
Pubic arch is greater than 90°
More space in the true pelvis (Table 8.1)
Jaycris C. Agnes , 2013
106. Skeleton of the Thigh - Femur and Patella
Femur - longest, heaviest, and strongest bone in the
body
Proximally, the head articulates with the acetabulum
of the hip bone forming the hip (coxal) joint
Neck - distal to head, common site of fracture
Distally, the medial and lateral condyles articulate
with the condyles of the tibia forming the knee joint
Also articulates with patella
Jaycris C. Agnes , 2013
107. Femur
Greater and lesser trochanters are projections
where large muscles attach
Gluteal tuberosity and linea aspera - attachment
sites for the large hip muscles
Intercondylar fossa - depression between the
condyles
Medial and lateral epicondyles - muscle site
attachments for the knee muscles
Jaycris C. Agnes , 2013
109. Patella
Largest sesamoid bone in the body
Forms the patellofemoral joint
Superior surface is the base
Inferior, narrower surface is the apex
Thick articular cartilage lines the posterior
surface
Increases the leverage of the quadriceps
femoris muscle
Patellofemoral stress syndrome - ―runner’s
knee‖
Jaycris C. Agnes , 2013
113. Skeleton of the Foot -
Tarsals, Metatarsals, and Phalanges
Seven tarsal bones - talus (articulates with
tibia and fibula), calcaneus (the heel bone,
the largest and strongest), navicular, cuboid
and three cuneiforms
Five metatarsals - (I-V) base, shaft, head
14 phalanges (big toe is the hallux)
Tarsus = ankle
Jaycris C. Agnes , 2013
115. Bone and Calcium Homeostasis
When blood calcium levels are too low,
osteoclast activity increases.
When blood calcium levels are too high
osteoblast activity decreases.
Jaycris C. Agnes , 2013
116. Bone and Calcium Homeostasis
Parathyroid hormones (PTH) – stimulates
increased bone breakdown and increased
blood calcium levels by indirectly stimulating
osteoclast activities.
Calcitonin – decreases osteoclast activity and
thus decreases blood calcium level.
Jaycris C. Agnes , 2013
118. Kinds of Joint based on movement:
Synarthrosis - non movable joints
e.g.- sutures
Amphiarthrosis - slightly movable joints
e.g.- rib cage
Diarthrosis - freely movable joints
e.g.-joints in the upper & lower limbs
Jaycris C. Agnes , 2013
119. Kinds of Joint based on structural
connection:
Fibrous Joints - consist of two
bones that are united by fibrous tissue and
that are united by fibrous tissue and that
exhibit little or no movement.
Jaycris C. Agnes , 2013
120. Sutures are fibrous joints between the bones
of skull.
Syndesmoses are fibrous joints in which the
bones are separated by some distance and
are held together by ligaments. An example
is the fibrous membrane connecting most of
the distal parts of the radius and ulna.
Gomphoses consist of pegs fitted into
sockets and held in place by ligaments. The
joint between a tooth and its sockets is a
gomphosis.
Jaycris C. Agnes , 2013
121. Cartilaginous Joints - unite two bones
by means of cartilage. Only slight movement
can occur at these joints
Examples are the cartilage in the
epiphyseal plates of growing long bones
and the cartilages between the ribs and
the sternum.
Kinds of Joint based on structural
connection:
Jaycris C. Agnes , 2013
122. Kinds of Joint based on structural
connection:
Synovial Joints -
are freely movable
joints that contain
synovial fluid in
cavity surrounding
the ends of
articulating bones.
Jaycris C. Agnes , 2013
123. Types of Joints
Hinge- A hinge joint allows extension and
retraction of an appendage. (Elbow, Knee)
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124. Ball and Socket- A ball and socket joint
allows for radial movement in almost any
direction. They are found in the hips and
shoulders. (Hip, Shoulder)
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125. Gliding- In a gliding or plane joint bones slide
past each other. Mid-carpal and mid-tarsal
joints are gliding joints. (Hands, Feet)
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126. Saddle- This type of joint occurs when the
touching surfaces of two bones have both
concave and convex regions with the shapes
of the two bones complementing one other
and allowing a wide range of movement.
(Thumb)
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128. Effects of aging on the Skeletal System
Bone matrix becomes more brittle and
decreases in total amount during aging.
Joints lose articular cartilage and become
less flexible with age.
Jaycris C. Agnes , 2013