Musculoskeletal System & Bioelectricity Quiz

Musculoskeletal System, Nervous System & Bioelectricity

• Subject: Musculoskeletal System, Nervous System & Bioelectricity
• Course: MNB.1 Skeleton, Bone, Ossification, Somatic Skeleton
• Lecturer: Dr. Tom Hodgkinson
• Date: 24th September 2024

Learning Outcomes

• Learners will be able to discuss the structure of bone and cartilage.
• Learners will be able to outline the different categories of the skeleton.
• Learners will be able to describe endochondral ossification.
• Learners will be able to recall the axial and appendicular skeleton, vertebrae, girdles, and limbs.
• Learners will be able to discuss the structure of different types of joints.
• Learners will be able to describe the detailed structure of the vertebral column.

Introduction to Bone Biology

• The vertebrate skeleton is composed of bone and cartilage for structural support.
• Bone is categorized into compact and spongy types.
• Compact bone forms the exterior of long bones, being dense and hard.
• Spongy bone is found internally in long bones and other bones, and forms a trabecular network between the marrow.
• Haversian systems comprise central Haversian canals housing blood vessels, surrounded by concentric lamellae containing osteocytes.
• Volkmann canals intersect these systems.

Bone Structure

• Lacunae are interconnected by canaliculi, facilitating nutrient supply to osteocytes.
• Bone undergoes constant remodeling and adaptation.
• Osteoclasts, a type of bone cell, are involved in bone erosion and resorption of damaged bone.
• Osteoblasts generate new bone extracellular matrix (approximately 80% calcium phosphate as calcium hydroxyapatite crystals, 20% organic protein, primarily type I collagen).

Bone Remodelling

• Bone remodelling is a continuous process of bone maintenance and adaptation.
• Bone growth during development can occur independently of osteoclast activity.

Periosteum and Endosteum

• Periosteum is a dense layer of vascular connective tissue covering bone; except at joints.
• It has outer fibrous and inner osteogenic layers.
• Endosteum lines the inner surface of the medullary cavity of long bones.
• It is a thin membrane of connective tissue.
• Osteoclasts remove bone from the endosteal ("inner") side.

Cartilage

• Cartilage functions include supporting soft tissues and providing low-friction surfaces at articulating joints.
• Three types of cartilage are discussed: hyaline, elastic, and fibrocartilage.
• Hyaline cartilage is common, found in articular surfaces.
• Elastic cartilage is flexible, in structures like the external ear.
• Fibrocartilage has a high collagen content, in the intervertebral disc.

Cartilage Structure

• Cartilage is semi-rigid and comprises an extracellular ground substance.
• This includes proteoglycans (e.g., Aggrecan), glycosaminoglycans (e.g., chondroitin sulfate and hyaluronic acid), and collagen (e.g., type II).
• Chondrocytes reside in lacunae in the cartilage matrix.

Structure of the Skeleton

• The skeleton can be categorized into dermal and endoskeleton types.
• Dermal skeleton development is different from the endoskeleton.
• The endoskeleton is initially formed from cartilage and further categorized into visceral (e.g., larynx cartilages) and somatic skeleton (remainder).
• Visceral skeleton refers to the cartilage present in structures such as larynx, tracheal cartilages, etc.

Somatic Skeleton

• The somatic skeleton is composed of both the axial and appendicular skeleton types.
• Axial skeleton comprises the skull, vertebral column, ribs, and sternum, highlighting regions like cervical, thoracic, lumbar, sacrum and caudal bones (coccix)
• Appendicular skeleton includes the pectoral (shoulder) and pelvic girdles; together with the bones of the upper limbs (humerus, radius, ulna, etc.) and lower limbs (femur, tibia, fibula etc.)
• Sesamoid bones, like the patella, develop in tendons.

Axial Skeleton - Vertebrae

• Cervical vertebrae are smaller, have transverse foramina and bifid spinous processes.
• Thoracic vertebrae are larger, have long spinous processes and facets for rib articulation.
• Lumbar vertebrae are the largest, with short, blunt spinous processes.
• The sacrum consists of fused vertebrae into a triangular shape.
• Caudal vertebrae, fused to form the tailbone, are small.

Vertebral Column

• The vertebral column has spinous processes, serving as muscle and ligament attachment points.
• Transverse processes are lateral projections for muscle and ligament attachment.
• Superior and inferior articular processes allow articulation with adjacent vertebrae.

Endochondral Ossification

• During fetal development, cartilage models the shape of future bones.
• Endochondral ossification is the process that converts cartilage to bone.
• The epiphyses of long bones, the ends, ossify last.
• The epiphyseal plate remains between the diaphysis and epiphyses until ossification is complete.

Endochondral Ossification - Genetic Condition

• Achondroplasia is one such genetic condition that affects the capacity for endochondral ossification, especially in long bones.
• Achondroplasia affects typical body growth processes.

Joints

• Joints are junction sites between two or more bones.
• Two fundamental types are non-synovial and synovial.
• Non-synovial joints connect bones by fibrous tissue (e.g., sutures of the skull) or cartilage.
• Synovial joints involve a joint cavity and specialized synovial membrane producing synovial fluid. This type allows significant range of motion.

Useful Reading

• Chapter 40 (838-842) of Biology, Solomon
• Chapter 39 on tissue types
• Chapter 10 (204-209) of Human Biology, Chiras