Unit 7: Skeletal System

Functions of the Skeletal System:

• Support and protection

• Body movement

• Blood cell formation = hematopoiesis  (occurs in bone marrow)

• Storage of inorganic materials (salt, calcium, potassium)

ORGANIZATION:

About 206 bones

with 2 Main Divisions 

It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together

Axial Skeleton:

• Head, neck, trunk

• Skull

• Hyoid Bone

• Vertebral Column

• Thoracic Cage (ribs, 12 pairs)

• Sternum

Appendicular Skeleton:

Pectoral Girdle (scapula, clavicle, arms)

Pelvic Girdle (coxal bones, legs)

- Fibrodysplasia ossificans progressiva(FOP)causes soft tissue (muscles, tendons, ligaments) to turn to bone. 

- Bone growth “flare-ups” often result from minor trauma to the tissue. 

BONE STRUCTURE - Long Bone:

1. Epiphysis (end)

2. Diaphysis (shaft)

3. Articular Cartilage 

    (hyaline cartilage, padding)

4.  Periosteum

     (membrane that covers entire bone)

5.  Medulla  (contains marrow)

The epiphyses are named according to their location.

The epiphysis closest to the body’s center is the PROXIMAL epiphysis.

The one that is farthest away is the DISTAL epiphysis. 

Inside the Long Bone:

1. Medullary Cavity – hollow, filled with yellow bone marrow

2. Endosteum– lines of the medullary cavity

3. Red Marrow - produces blood 

4. Yellow Marrow - fat storage

Types of Bones:

Types of Bone Tissue:
Compact (wall of the diaphysis)

Spongy (cancellous, epiphysis) - red marrow

Microscopic Structure:

Bone tissue is called OSSEOUS tissue
  - the matrix is composed of collagen and inorganic materials like calcium and phosphate

OSTEOCYTES  - mature bone cells, enclosed in tiny chambers called LACUNAE

• these form rings called LAMELLAE  around 

• HAVERSIAN CANAL which houses blood vessels

CANALICULI - tiny canals that link osteocytes

Bone Development:

- Bones first form as hyaline cartilage, then gradually changes into bone tissue - a process called OSSIFICATION

• PRIMARY OSSIFICATION CENTER - increases diameter

• SECONDARY OSSIFICATION CENTER - increases length

OSTEOBLASTS: create osteocytes.

OSTEOCLASTS: bone resorption

Bone Growth:

- EPIPHYSEAL DISK  (growth plate) is a band of cartilage between the epiphysis and diaphysis

• Bone growth in FOP cases is likely due to a mutation in a gene that codes for BMP - bone morphogenetic protein. 

• As a result, the receptor stays in an “on” state

• Noggin and gremlin are inhibitors of BMP signaling

Types of Joints (articulations):

- Synarthrotic - immovable joint, called sutures,  skull

- Amphiarthrotic - slightly movable → vertebrae

- Diarthrotic - moveable joint → knees, elbows, wrist, shoulder..etc
(also called synovial joints)

Types of Diarthrotic Joints:

1.  Ball and Socket (shoulder / hip)

2.  Hinge (elbow, knee)

3.  Pivot (lower arm)

4.  Saddle (thumb)

Sutures: connection points:

1. Coronal - between frontal and parietal bones

2. Lambdoidal - between occipital and parietal bones

3. Squamosal - between temporal and parietal bones

4. Sagittal - between parietal bones

Fontanels are “soft spots” on an infant’s skull

Topography of the Skull:

Foramen - refers to any opening in the skull, nerves and blood vessels leave this opening to supply the face

Vertebral Column:

Cervical(C1-C7)

Thoracic(T1-T12)

• Thoracic Cage →  12 pairs of ribs

  • True Ribs = First seven

  • False Ribs = Next 3 pairs

  • Floating Ribs = Last two pairs

Lumbar(L1-L5)

Sacrum and Coccyx(tailbone)

Pectoral Girdle:

CLAVICLES:(collarbones)

SCAPULAS:(shoulder blade)

Problems with the Skeletal System:

1. Bone Spurs

   - also known as osteophytes, occur when the body grows small projections on the edges of bones

2. Plantar fasciitis 

   - common cause of heel pain.  

   - inflammation of the plantar fascia

   - walking can be painful

3. Osteoporosis

   - Increased activity of osteoclasts cause a break down bone, bones become more fragile 

   - The spongy bone especially becomes more porous. 

   Causes:

   • Lack of exercise

   • Poor diet

   • Genetics

   • Ethnicity

   • Gender

   - Why do older people break their hips? A femoral neck fracture is common among  older adults and can be related to osteoporosis. This  type of fracture may cause a complication because the break usually cuts off the  blood supply to the head of the femur. 

4. Rheumatoid arthritis

   an autoimmune disease which causes joint stiffness and bone deformity

5. Rickets

   Deficiency of Vitamin D. Rickets causes weak, brittle bones that fracture easily and affect growth.

6. Nursemaid’s Elbow 

   -subluxation
   -pulling on arm separates bones

   -ligament slides between humerus and radius

7. Shoulder Dislocation

   -results from force or trauma

   -humerus pops out of socket

8. Fibrodysplasia ossificans progressiva (FOP)

    soft tissue regrows as bone. 

9. Osteosarcoma

   Most common bone cancer, primarily affecting the long bones, particularly those in the knee, hip, or shoulder regions.   Most commonly affects teenagers and young adults.

Abnormalities of the Spine:

A. Kyphosis: is a hunchback curve

B. Lordosis: is a swayback lower region.

C. Anklylosis: