Skeletal System

Chapter 1: Introduction

  • Objective of today's session:

    • Discuss the functions of the skeletal system

    • Distinguish the difference of axial and appendicular skeleton

    • Identify the parts of a typical long bone

    • Describe the different types of joints found in the body

    • Describe the specific types of bone fracture

    • Understand and distinguish the different disorders of the skeletal system

Rickets is a condition that affects bone development in children, typically caused by a deficiency in vitamin D, calcium, or phosphate. It leads to weak and soft bones, resulting in skeletal deformities. Treatment usually involves vitamin D and calcium supplementation, along with exposure to sunlight.


Skeletal System Introduction

  • Parts of the skeletal system:

    • Bones

    • Cartilage

    • Ligaments

  • Interaction of bones, cartilage, and ligaments in joints

  • Two types of division in the skeletal system:

    • Axial skeleton

    • Appendicular skeleton

Overview of the Skeleton

  • Frontal bone, nasal bone, temporal bone, zygomatic bone, and mandible are part of the skull

  • Parietal bone, temporal bone, occipital bone, and sphenoid bone are part of the superficial bones of the skull

  • Vertebral column consists of cervical, thoracic, lumbar, sacral, and coccygeal vertebrae

  • Sternum and ribs are part of the thoracic cage

  • Extremities include the upper and lower limbs

Functions of Bones

  • Support the body and provide structure

  • Protect soft organs

  • Allow movement and locomotion

  • Store minerals like phosphate and calcium, as well as fat

  • Site of hematopoiesis (blood cell formation)

Types of Bones

  • Long bones: longer than wide, have a shaft with heads at both ends (e.g., femur, humerus)

  • Short bones: roughly cube-shaped (e.g., carpal bones)

  • Flat bones: thin and flattened (e.g., skull, ribs)

  • Irregular bones: do not fit into the other categories (e.g., vertebrae)

  • Each bone has a diaphysis (shaft) and epiphysis (ends)

  • Long bones have an epiphyseal line or plate

Chapter 2: New Bone Tissue

  • Hyaline cartilage is present during growth and development

    • Articular cartilage is responsible for articulation in joints

  • Periosteum is the tissue that covers the bone

    • It is a connective tissue that contains blood vessels

  • Short bones are generally cube-shaped and contain mostly spongy bone

    • Examples include carpals and tarsals

  • Flat bones are thin and flattened, usually curved

    • They consist of thin layers of compact bone surrounding a layer of spongy bone

    • Examples include the skull, ribs, and sternum

  • Irregular bones do not fit into the categories of long, short, or flat bones

    • They are irregular in shape and are found in the vertebrae and hip

  • Osteocytes are cells found in compact bone responsible for exchanging minerals and communicating with each other through canaliculi

    • Osteocytes are formed from old osteoblasts that have become trapped in the bone matrix

  • Osteoblasts are cells that create new bone or repair existing bone

    • They create a flexible material called osteoid, which is then fortified with minerals to make the bone hard and strong

  • Osteoclasts are responsible for breaking down existing bone material and reshaping the bone

    • They also play a role in bone healing and remodeling

  • Bone tissue is composed of cortical (compact) bone and trabecular (spongy) bone

    • Cortical bone is the hard outer shell of bone, while trabecular bone is the spongy center

  • Osteons are the basic units of cortical bone and are composed of concentric lamellae

    • Osteocytes are distributed within the lamellae and play a role in maintaining bone integrity

  • Trabecular bone resists compression and contains osteocytes

    • Lining cells cover the trabeculae and are involved in the formation and breakdown of bone

  • Bone marrow is found within the interior of bones and is a site for hematopoiesis (blood cell formation)

  • Bone remodeling is the process of building, breaking down, and rebuilding bone tissue

    • Osteoclasts break down bone tissue, while osteoblasts build new bone tissue

  • Bone tissue serves as a repository for minerals and biologically active molecules

    • Calcium phosphate is a vital mineral stored in bone

  • Osteoblasts produce the organic component of bone (osteoid) and mineralize it with calcium phosphate to form hydroxyapatite

  • Bone mineral density (BMD) is used to estimate bone strength and assess fracture risk

  • Osteoblasts differentiate into osteocytes and become embedded within the bone matrix

  • Bone growth occurs through epiphyseal plates, which allow for the growth of long bones

    • Epiphyseal plates are areas of cartilage that become ossified over time

Chapter 3: Broken Bone Portion

  • Importance of cartilage in bone growth and development

    • Cartilage changes or ossifies to become new bone

    • Bones are remodeled and strengthened until growth stops

    • Bones change shape somewhat during growth

  • Bone fractures

    • Break in a bone

    • Types of bone fractures: closed and open

      • Closed fractures: simple fracture, skin remains intact

      • Open fractures: broken bone penetrates the skin

    • Fractures treated by reduction and immobilization to reduce movement

  • Common types of fractures

    • Comminuted fractures: bone breaks into many pieces

    • Compression fractures: bone is crushed

    • Impacted fractures: broken bone ends are forced into each other

    • Greenstick fractures: bone breaks incompletely, common in children

  • Repairing bone fractures

    • Hematoma forms within the fracture area

    • Fibrocartilage splints the break to form a callus

    • Callus is replaced by bony callus, which becomes the permanent patch for the damaged bone

    • Remodeled bone forms over months

Bone Remodeling and Bone Formation

  • Bone changes across the human lifespan

    • Bone formation and growth in childhood

    • Gradual loss of bone density in early adulthood and older adults

    • Modulation of bone density by osteoclasts and osteoblasts

  • Bone remodeling process

    • Osteoclasts resorb bone by creating an acidic environment and removing mineral content

    • Osteoblasts refill the resorption cavities with organic matrix called osteoid

    • Osteoid provides a scaffold for mineral crystallization

    • Some osteoblasts become osteocytes, while others undergo apoptosis or revert back to lining cells

    • Remodeling involves both bone resorption and formation

    • Bone modeling can occur without prior resorption, promoting bone growth and strength

  • Factors influencing bone remodeling and loss

    • Medications, such as glucocorticoids, can promote osteoclast activity and reduce bone formation

    • Proper nutrition and physical activity help strengthen bone

    • Osteocytes sense increased workload on bone and trigger osteoblast activity

    • Reduced loading conditions increase resorption and remodeling, leading to bone loss and increased fracture risk

    • Importance of staying active, maintaining good nutrition, and being aware of personal risk factors for low bone density

The Skeleton and Bone Structure

  • Two groups of the skeleton: axial and appendicular

  • Axial skeleton includes the skull, vertebral column, and rib cage

  • Skull is made up of the cranium and facial bones, joined by sutures

  • Only movable joint in the skull is the mandible

  • Bones of the skull include parietal, frontal, occipital, and temporal bones

Chapter 4: Support Frontal Bone

  • External auditory meatus

    • Mastoid process in the temporal bone

    • Muscle called sternocleidomastoid attached to the clavicle

    • Movement muscle important for mastoid process

    • Styloid process

  • Zygomatic process

    • Cheek muscle called zygomaticus major

    • Protruding bone marking from the main shape of the nebular bone

  • Mandible

    • Ramos of the mandible or mandibular ramus

    • Mental foramen (cheek/chin)

  • Maxilla

    • Attachment point for upper teeth

    • Areolar processes

  • Lacrimal bone

    • Tears and lacrimal gland

  • Ethmoid bone

    • Posterior portion

  • Medical sphenoid

    • Base of the orbit

  • Bones that surround the orbital cavity

    • Ethmoid bone

    • Zygomatic bone

    • Frontal bone

    • Maxilla

    • Sphenoid bone

  • Sutures

    • Coronal suture (frontal and parietal bones)

    • Squamous suture (temporal and parietal bones)

    • Lambdoid suture (occipital and parietal bones)

    • Sagittal suture (joins the parietal bones together)

    • Transverse palatine suture (palatine bones to maxilla)

    • Coronal suture (frontal bone and two parietal bones)

  • Foramen magnum

    • Base of the skull

    • Passage for spinal cord and brainstem

  • Other bone markings

    • Foramen ovale

    • External and internal auditory meters

Chapter 5: Parietal Bone Portion

  • Classification of bone:

    • flat bone, short bone, irregular, long bone

  • Facial bones:

    • Frontal bone

    • Parietal bone

    • Temporal bone

    • Zygomatic bone

    • Maxilla

    • Nasal bone

    • Mandible

    • Vomer

  • Septum and nasal concha

  • Bone markings and orbital cavity

  • Base of the skull and maxilla

  • Palate and sphenoid bone

  • Nasal sinuses and sinusitis

  • Functions of paranasal sinuses

  • Hyoid bone and its functions

Vertebral Column

  • Curvature of the vertebral column

  • Cervical, thoracic, lumbar, sacral, and coccyx bones

  • Classification of vertebral column

  • Cervical vertebrae (C1-C7)

  • Thoracic vertebrae (T1-T12)

  • Lumbar vertebrae (L1-L5)

  • Intervertebral discs and fibrocartilage

  • Ribs and their classification

  • Structure of vertebrae

  • Normal and abnormal curvatures of the spine

  • Axial skeleton and the thoracic cavity

  • Ribs and their functions in the cardiorespiratory system

Chapter 6: Pelvic Bone Head

  • Ribs are attached to the vertebrae via cartilage

    • True ribs are directly connected to the sternum

    • Floating ribs (11 and 12) are not connected to the sternum

  • The sternum consists of the manubrium, sternal body, and xiphoid process

  • CPR involves compressions on the sternum to pump blood

  • The appendicular skeleton includes the upper and lower extremities

  • The pectoral girdle is composed of the clavicle and scapula

  • The upper limb consists of the humerus, radius, and ulna

  • The forearm allows for supination and pronation

  • The carpal bones are short bones in the hand

  • The metacarpals are the bones in the palm

  • The phalanges are the bones in the fingers

  • The hip bone is made up of the ilium, ischium, and pubic bone

  • The pelvic bones protect reproductive and urinary organs

  • The acetabulum is the socket for the head of the femur in the pelvic bone

  • The lower limb includes the femur, trochanters, and diaphysis

Chapter 7: Pelvic Bone Acetabulum

  • Left and right sides of the pelvic bone acetabulum are being discussed

  • The structure of the left and right sides is being saved

  • Different views of the femur and pelvic bone acetabulum are being examined

  • The left and right sides are being pointed out and identified

Lower Portion of the Leg

  • The tibia and fibula bones are discussed

  • The bones of the foot, including the tarsus and toes, are mentioned

  • The different bones of the tarsus are listed, including the cuneiform, navicular, and intermediate bones

  • The proximal, distal, and middle parts of the foot are described

Joints

  • Joints are the points where bones are connected

  • The function of joints is to hold bones together and allow mobility

  • Joints can be classified functionally as synarthrosis, amphiarthrosis, or diarthrosis

  • Synarthrosis joints are immovable, amphiarthrosis joints are slightly movable, and diarthrosis joints are freely movable

  • Examples of different types of joints are given, including sutures, syndesmosis, and symphysis

Structure of Joints

  • Joints can also be classified based on their structure

  • Fibrous joints are made up of thick fibrous material and are generally movable

  • Cartilaginous joints are immovable or slightly movable

  • Synovial joints are free-moving and have synovial fluid and articular cartilage

  • Features of synovial joints are described, including the synovial membrane, articular cartilage, bursae, and tendon sheath

Conclusion

  • Inflammation of the bursa is called bursitis, inflammation of the tendons is called tendinitis, and inflammation of the joint is called arthritis

  • Bone remodeling, bone fractures, and diseases like arthritis are discussed

  • The importance of understanding and organizing the terminology related to bones and joints is emphasized

  • The human skeleton consists of 206 bones