2. Learning objectives
Students should be able to describe the histology of bones and bone types
Students should be able to describe the gross anatomy of bones
Students should be able to classify joints with examples
Students should be able to describe high-yield clinical correlates
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3. INTRODUCTION
o Hard connective tissue
o ≈30% organic matrix made of
collagen fibers, proteoglycan gel
(amorphous ground substance) and
osteonectin
o ≈70% is a mixture of inorganic salts
(hydroxyapatite) rich in calcium
phosphate crystals
o very little percentage of bone cells
Functions
1. Support
2. Give form and shape
3. Protection
4. Facilitate movement
5. Facilitate hearing with the aid of the 3
ossicles
6. Site for production of blood cells
7. Storage - calcium, phosphate and
triglycerides (fat, specifically in the yellow
bone marrow)
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4. Types of bone
Compact/lamella/cortical bone –
hard; precisely structured; Osteon or
Haversian system
Spongy/cancellous bone - sponge-
like arrangement of trabeculae;
surrounds the medullary cavity of long
bones; surrounded by a layer of
compact bone.
Bone classification
1. Long bones – a shaft (diaphysis) and 2 ends
(epiphyses). Between the diaphysis and each
epiphysis of an adult long bone is an epiphyseal
line.The shaft has a medullary cavity
containing bone marrow. E.g., humerus, ulna,
radius, femur, tibia, fibula, metacarpals and
metatarsals.
2. Short bones – carpals and tarsals.
3. Flat bones – cranium, ilium, sternum, ribs.
4. Irregular bones – they have projections on
their surfaces. E.g., vertebrae and facial bones
5. Sesamoid bones –They reduce friction in
tendon. Largest is the patella 4/10/2023
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5. Gross arrangement of bone structure
Wrapped with double layers of fibrous vascular
tissue, periosteum (collagen fibers)
Inner layer of the bone is single-layered endosteum
(reticular connective tissue)
Long bones have a centrally placed medullary
cavity that contains the bone marrow
Thin layer of articulating cartilage at the epiphyses
One or two oblique nutrient foramina in the shaft
for blood vessels
Scanty lymphatics; innervated
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6. Structural unit made of concentric
arrangement of lamella
At the center of each osteon is the
central or haversian canal
Between the lamella are lacunae
which contain osteocytes that
communicate with themselves and
with blood vessels via the canaliculi
Haversian system/Osteon
(compact bone)
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7. Through Volkmann’s canal,
central canal communicate with
themselves and medullary cavity.
Interstitial lamellae fill the space
between osteons
Circumferential lamellae extend
around the entire circumference
of the diaphysis
Haversian system/Osteon
(compact bone)
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9. BONE OSSIFICATION/DEVELOPMENT/OSTEOGENESIS
All bones are derived from mesenchyme formed from paraxial mesoderm except
the neurocranium and viscerocranium from neural crest cells.
Most bones take many years to become mature and they start to form during
embryonic period (flat bones) after the embryonic period (other bones).
Intramembranous ossification for flat bones and clavicle
Endochondrial (cartilaginous) ossification for long, short, irregular bones
Fibroblast growth factors (FGFs) and Fibroblast growth factor receptors (FGFRs;
FGFR 1, FGFR 2, and FGFR 3) play vital role in bone ossification as they regulate
proliferation, differentiation and migration.
Hereditary, Hormones, Nutrition, and Exercise affect bone growth and maintenance
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10. Endochondrial ossification
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Intramembranous ossification
Some selected mesenchymal cell cluster
and differentiate into osteoblasts.
Calcification of bone matrix (collagen
fibers) secreted from osteoblasts
Trabeculae formation- woven bone and
periosteum form
Compact bone replaces woven bone
below the periosteum and red bone
marrow appears
11. Articulating surface
Condyle A large round articulating knob
or protuberance (med. and lat.
condyles of the femur)
Facet A flattened or shallow
articulating surface usually small
(facets on the vertebrae)
Head A prominent, rounded
articulating end of a bone (head
of humerus, femur)
Trochlea spool-like articulating process (in
humerus)
Capitulum small, round, articular head (in
humerus)
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Depression and openings
Fissure A narrow slit (sup./inf. orbital fissure
of the sphenoid bone)
Foramen A rounded opening through a bone
(foramen magnum)
Fossa A hollow or depression (olecranon
fossa of the humerus)
Groove Elongated furrow (radial groove of
humerus)
Sinus A cavity or hollow space in a bone
(frontal sinus of the frontal bone)
Sulcus A groove that houses a blood vessel,
nerve or tendon (intertubercular
sulcus)
12. 4/10/2023
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Non-articulating prominences
Epicondyle Projection adjacent to the condyle (medial and lateral condyle of the
femur)
Crest A narrow ridge like projection (iliac crest of the ilium)
Process Any marked prominence (spinous process, mastoid process)
Spine Sharp ridge of bone (spine in scapula)
Trochanter A massive process found only in the femur (greater and lesser)
Tubercle A small rounded process (greater and lesser in humerus0
Tuberosity A large roughened process (radial/ulna tuberosity of the ulna and radius)
13. SKELETON
Axial skeleton
Bones in the head, neck and the trunk; skull,
auditory ossicles, hyoid bone, vertebrae,
sternum and ribs.
Appendicular skeleton
Bones in the shoulder, hip, upper and lower
extremities; scapular, clavicle, humerus,
ulna, radius, carpals, metacarpals,
phalanges, pelvic bones, femur, patella,
tibia, fibula, tarsals, metatarsals and digits. 4/10/2023
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14. Axial skeleton
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SKULL
Neurocranium - 8 bones: 1 frontal, 1 occipital,
1 sphenoid, 1 ethmoid, 2 parietal &2 temporal
Viscerocranium - 14 bones: 2 zygomatic, 2
maxillae, 2 nasal, 2 lacrimal, 2 palatine, 2
inferior nasal conchae, 1 vomer and 1
mandible.
HYOID BONE: a single floating bone in the
neck above the thyroid cartilage.
AUDITORY OSSICLES: malleus (hammer),
incus (anvil) and stapes (stirrup).Three small
bones found in the each middle ear cavity.
15. STERNUM: Flat and elongated bone; manubrium, body and
xiphoid process. On its lateral borders are facets for
sternoclavicular joints, 1st - 7th coastal cartilages.
VERTEBRAL COLUMN: Base of the skull to the coccyx; 33
vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral bones
fused to become 1 sacrum, and 4 caudal vertebrae fused to
form a coccyx); spinal cord runs in vertebral canal.
RIBS: Lateral wall of the thorax; 12 pairs of rib; C-shaped;
extend from the vertebrae posteriorly to the coastal
cartilages that enter the sternum anteriorly. A rib could be
typical (3rd – 9th) or atypical (1st, 2nd, 10th, 11th and 12th). True
ribs, false ribs and floating ribs. 4/10/2023
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16. Appendicular Skeleton
CLAVICLE (collar bone): Slightly ‘S’ shaped and
somewhat flattened; it has 2 ends (round
medial/sternal end and flattened lateral/acromial
end). Easily fractured in children
SCAPULA (shoulder blade): Flat; triangular; posteriorly
overlies the ribs 2-7; a broad coastal surface
(subscapular fossa); posterior surface marked by a ridge
(spine of scapular). On the lateral angle are:
1. Acromion: Plate-like extension of the spine
2. Coracoid process: like a bent finger extending from
the lateral end of the suprascapular notch.
3. Glenoid cavity: a shallow socket for the head of
humerus.
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17. HUMERUS: bone of the arm; long bone; a
hemispherical head that forms glenohumeral
joint with the glenoid cavity of scapula; it
forms elbow joint with the ulna and radius
distally. Fracture mostly at the surgical neck,
mid-shaft and distal end.
ULNA and RADIUS: bones of the forearm;
ulna is longer and medial to the radius; radius
has a tapper head.These bones are held
together by the interosseous membrane,
proximal and distal radioulnar joints.
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18. CARPALS (wrist bones): 8 short bones
arranged in two rows:
proximal row- from medial to lateral: pisiform,
triquetrum, lunate, scaphoid (PTLS)
distal row- from medial to lateral: hamate,
capitate, trapezoid, trapezium (HCTT)
METACARPALS
5 metacarpals are found in the palm and they
are numbered from lateral (1st) to medial (5th)
PHALANGES (finger bones)
14 phalanges; 3 in each finger (proximal,
middle and distal) except the thumb with 2
(proximal and distal). 4/10/2023
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19. Pelvic bone
Made of 3 fused inanimate bones; ilium,
ischium and pubis.
The ilium is the largest and it occupies the
upper part. It has 4 spines, a gluteal surface
and a medial surface that presents the iliac
fossa.
The pubis is place anteroinferiorly
The ischium is posteroinferiorly placed
Acetabulum is located laterally for the head
of femur
Below the acetabulum is the obturator
foramen
The hip bone unites with the sacrum and
coccyx at the sacroiliac joint 4/10/2023
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20. Bone of sexual dimorphism Pelvis
Parameters Male pelvis Female pelvis
Size Short and narrow with heavy and thick
bones
Large and wide with light and dense bones
Sacrum Long and narrow Wide and shorter, less curved
Pubic Arch V-shaped Wider
Sciatic Notch Narrower Wider
Purpose
Supports the heavy body and muscles of the
men
Supports, childbearing and the easier child
delivery
Pelvic Outlet Narrower Wider
Pelvic Inlet Heart-shaped Slight oval shaped
Acetabulum Larger Smaller
Coccyx
It is projected inwards (less curved anterior)
and immovable.
Flexible and straight
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22. Femur: the longest and heaviest bone. It has an
almost spherical head, a neck below the head
directed inferiorly, laterally and anteriorly.
Extending from the neck are the lateral greater
and medial lesser trochanters.
The shaft has a smooth anterior surface and a
posterior surface marked by linea aspera
Tibia and fibula: The thick tibia is medial to the
slender fibula.
The fibula has a neck below the apex and head
These bones are held together by the
interosseous membrane, proximal and distal
tibiofibular joints.
The distal ends of tibia and fibula have malleoli.
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23. 4/10/2023
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Patella (kneecap):This is the largest sesamoid
bone and it is roughly triangular in shape. It is
associated with the knee joint anteriorly.
Tarsal (ankle) bones: 7 bones that form the
posterior part of the foot.Talus, calcaneus,
navicular, cuboid and cuneiforms.Talus form
ankle joint with the tibia, while calcaneus form
the heel.
Metatarsals (Bones of the feet): 5 bones
numbered from medial to lateral. It forms the
major part of the sole of the foot.
Phalanges/Digits (Toe bones): 14 bones
aligned as the phalanges in the fingers.
24. Joint
Fibrous joint (synarthrosis/synarthrosial joint)
Sutures- serrated, lap or plane maxillae sutures
Gomphoses teeth and sockets.
Syndesmoses interosseous membrane
Cartilaginous joint amphiarthrosis/amphiarthrosial joint
a. Symphysis: the bones are held by fibrocartilage e.g., public symphysis
Synchondroses: epiphyseal plate, manubrium/body of sternum
Synovial joint (diathrosis/ diarthrosial joint)
Ball and socket joint: shoulder and hip joints
Hinge joint: elbow and knee joints
Gliding joint: joint between carpals and tarsals.
Pivot joint:
Condylar joint (ellipsoid): temporomandibular joint
Saddle joint: trapezometacarpal joint 4/10/2023
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25. Fracture
Simple or closed: broken ends do not
pierce the skin
Compound or open:
Complete if the bone breaks into two or
more pieces
Incomplete if it is a partial fracture
Nondisplaced if the bones are still in their
anatomical position
Displaced:
Comminuted if the bone is shattered into
three or more pieces
Linear,Transverse, and Oblique 4/10/2023
25 Common pediatric fractures
1. Epiphyseal fracture if it is at the
epiphyseal plate
2. Greenstick fracture if bone is bent on
one side and has incomplete fracture at
the other side, due to bending stress
3. Torus fracture if axial pressure exert on
the axis of the long bone causing a
buckle fracture
26. Colles fracture: complete transverse fracture of the distal 2cm of the radius; common
among ≥ 50 year-old-adults., more in women secondary to osteoporosis; most common
fracture of the forearm.The distal fragment displaced dorsally and is often comminuted.
Unhappy triad (blown knee): Tear of the anterior cruciate ligament, posterior cruciate
ligament and medial meniscus when a lateral force is exerted on a fixed leg. Acute pain and
poor knee stability
Housemaid’s knee (Prepatellar bursitis)
Baker’s cyst: Fluid collection in the popliteal region in gastrocnemius-semimembranosus
bursa; it communicates with synovial space and related to chronic joint disease
Medial epicondylitis (golfer’s elbow due to forehand shots) and lateral epicondylitis (tennis
elbow due to backhand shots)
Achondroplasia: defective endochondrial ossification causing short limbs (dwarfism).This is
due to mutation of FGFR3 in 4p16 inhibiting the proliferation of chondrocytes. Most common
dwarfism; large head
4/10/2023
27. Loss of bone density.The femoral neck, vertebral centrum,
metacarpals, and radius are most affected.Vertebral body
osteoporosis can cause vertebral compression fracture and
vertebral kyphosis.
Causes: primarily due to ↑ bone resorption related to old
age and ↓ oestrogen level or secondarily due to drugs
(alcohol, anticonvulsants, steroid, anticoagulants) or other
medical conditions (hyperparathyroidism,
hyperthyroidism, multiple myeloma [monoclonal plasma
cell cancer in the marrow]).
Diagnosis: Bone mineral density scan (DEXA withT-score ≤
−2.5 or a fragility fracture of the hip or vertebra.
Prevented by regular weight-bearing exercise and
optimum Ca2+ and vit. D in diet.Treatment:
bisphosphonates, teriparatide, denosumab, Selective
estrogen receptor modulators (SERMs).
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Osteoporosis
28. Osteopetrosis
Abnormal ↑ in bone density making the
bone easy to brittle.
Defective osteoclasts unable to resorb
bone matrix causing overgrowth and
sclerosis, as osteoblast out-function
osteoclasts.This can narrow foramina
as such compressing cranial nerves
causing CN palsies.
Medullary cavity or trabeculae spaces in
spongy bones are filled with bone
causing pathologic extramedullary
hematopoiesis due to pancytopenia
(low levels of blood cells). 4/10/2023
28
Osteomalacia
Softening of due to inadequate
vitamin D or mineralization causing ↓
phosphate and calcium. It is called
rickets in children and it can lead to
pathologic genu varum (bow-leg) later
in life.
Costochondrial junctions appear like a
beads (rachitic rosary); epiphyseal
widening are seen in x-ray.
Increased parathyroid hormone is also
implicated here.
29. Osteonecrosis (avascular necrosis)
A very painful condition that is involved with
insufficient blood supply (infarction) to bone
and marrow especially at the femoral head
(due to insufficiency of medial circumflex
femoral artery anastomosing with a branch of
obturator artery on the femoral head).
Caused by CAST Bent LEGS -
Corticosteroids, Alcoholism, Sickle cell disease,
Trauma, “the Bends” (caisson/ decompression
disease), LEgg-Calvé-Perthes disease
(idiopathic), Gaucher disease, Slipped capital
femoral epiphysis
4/10/2023
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30. 4/10/2023
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Rheumatoid arthritis Autoimmune-inflammatory disease forming
pannus that erodes articulating cartilage and bone
Predisposing factors:
Female
Smoking
silica exposure
HLA-DR4 (a genetic anomaly found in WBCs)
high Rheumatoid Factor (IgM targets Fc
fragment of IgG; in 80%) above 20IU/ml
Presentation: Pain, swelling, and morning
stiffness lasting over 1 hour (improve with use).
Symmetric joint involvement. Systemic symptoms
(fever, fatigue, weight loss). Extraarticular
manifestations common– rheumatoid nodules in
subcutaneous tissue, interstitial lung disease,
pleuritis, pericarditis.
32. Osteoarthritis Degenerative joint disorder caused by
mechanical wear and tear of articulating
cartilage leading to friction in the joint with
excruciating pain and inflammation with poor
repair.
Predisposing factors: Age, female, obesity,
joint trauma
Presentation: knee, hip and back pain in
mostly at night but it improves with rest.
Joint findings: Osteophytes (bone spurs), joint
space narrowing, subchondral sclerosis and
cysts. Synovial fluid non-inflammatory
WBC<2000/mm3.Involves DIP (Heberden
nodes) and PIP (Bouchard nodes), and 1st
CMC; not MCP.
Treatment: Acetaminophen, NSAIDs, intra-
articular glucocorticoids
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33. Seronegative spondylarthritis
Arthritis without rheumatoid factor but with strong association with HLA-B27
Human LeukocyteAntigens (HLAs) are proteins that helps the body immunity to
differentiate one’s cells from foreign cells.
Subtypes of seronegative spondyloarthritis are PAIR – Psoriatic arthritis, Ankylosing
spondylitis, Inflammatory bowel disease (IBD) – associated arthritis (enteropathic
arthritis), and Reactive arthritis. All usually affect the vertebra (back pain)
All are responsive to NSAID to relief pain, if not, then glucocorticoids DMARDs
(disease-modifying antirheumatic drugs).
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34. 4/10/2023
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Ankylosing spondylitis
More common in young males , symmetric involvement
of spine and sacroiliac joints causing joint fusion
(ankylosis), uveitis, aortic regurgitation.
Bent and fused spine (bamboo-like) causing poor chest
expansion due to costovertebral and costosternal
ankylosis leading to restrictive lung disease.
Psoriatic arthritis
Associated with psoriasis and nail bed pitting (onycholysis). < 1/3 psoriatic
patients have this. Presentation : asymmetric and patchy involvement. Dactylitis
and “pencil-in-cup” deformity of DIP on x-ray.
35. 4/10/2023
35
Inflammatory bowel disease such as Crohn disease and ulcerative colitis are often
associated with spondyloarthritis i.e. enteropathic arthritis is secondary to
inflammatory bowel disease.
Reactive arthritis (Reiter syndrome)
Caused by infections; Shigella,Yersinia, Chlamydia, Campylobacter
Symptoms - classic triad: Conjunctivitis, Urethritis, and Arthritis. Patients complain
“can’t see, can’t pee, can’t bend my knee”
Septic arthritis
Cause: commonly caused by Staphylococcus aureus,
Streptococcus, and Neisseria gonorrhoeae.
Presentation: swollen, red, and painful joint. Joint
finding: synovial fluid purulent (WBC > 50,000/mm3).
Gonococcal arthritis - STI that presents as either purulent
arthritis (e.g., knee) or triad of polyarthralgia,
tenosynovitis (e.g., hand), dermatitis (e.g., pustules).
36. Gout Acute inflammation monoarthritis caused by deposition of
uric acid in the form of monosodium urate in a joint
Uric acid deposition is due to hyperuricemia due
underexcretion (90%; idiopathic or due to renal failure) or
overproduction (10% ; Lesch-Nyhan syndrome, PRPP excess).
Symptoms: Asymmetric, swollen, red and painful joint.
Evident symptom is painful metatarsophalangeal joint of the
big toe. Tophus formation on external ear, olecranon bursa, or
Achilles tendon. A large meal food with plenty red meat and
seafood (rich in purines) tends to initiate an acute attack.
Trauma, surgery, dehydration, diuresis, or alcohol
consumption (alcohol compete with uric acid excretion). Gout
is common in males
Treatment: Acute - NSAIDs (e.g., indomethacin),
glucocorticoids, colchicine. Chronic (preventive): xanthine
oxidase inhibitors (e.g., allopurinol, febuxostat).
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birefringent needle-like
37. Primary bone tumors
Benign tumours
Osteochondroma – bony exostosis (bony growth
covered with cartilage). Most common benign bone
tumour; common among males over 25 years.
Giant cell tumour – common at epiphysis of long bone
(distal femur and proximal tibia);appear like soap-bubble
on x-ray; both gender 20-40 years..
Malignant tumours
Osteosarcoma (osteogenic sarcoma) – very common;
10-20 years and >65 years prevalence. Predisposing
factors are Paget disease of bone, radiation, dead tissue
(infarcts) in bone. Often around knee at the metaphysis.
Surgery and chemotherapy
Ewing sarcoma - diaphysis of long bones, pelvis, scapula
and ribs; boys below 15 years old. Extremely aggressive;
early metastases; but responsive to chemotherapy. 4/10/2023
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