Chapter 38: The Musculoskeletal System

What are the primary functions of the musculoskeletal system?

Support, maintaining upright posture, allowing movement (body transport and object manipulation), and protection.

Hydrostatic skeleton

A skeleton formed by a fluid-filled compartment within the body called the coelom, which is under hydrostatic pressure to support organs.

Which types of animals typically possess a hydrostatic skeleton?

Soft-bodied invertebrates such as sea anemones, earthworms, and Cnidaria.

Exoskeleton

An external skeleton that consists of a hard encasement on the surface of an organism.

What are the main functions of an exoskeleton?

Providing defense against predators, supporting the body, and allowing movement through muscle contraction.

What is the primary material found in the exoskeleton of arthropods?

Chitin, a polysaccharide derivative of glucose.

Endoskeleton

A skeleton consisting of hard, mineralized structures located within the soft tissue of an organism.

Axial bones

Bones down the midline

Highway bones

Bones that help support the larynx

Auditory ossicles

Bones that help communicate sound

What bones comprise the human axial skeleton?

The bones of the skull, ossicles of the middle ear, hyoid bone, vertebral column, and rib cage.

What are the two main functions of the skull bones?

Supporting the structures of the face and protecting the brain.

List the components of the human vertebral column.

Seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, the os sacrum, and the coccyx.

Lordosis

An exaggerated inward curve of the lumbar (lower back) or cervical (neck) spine, often causing a "swayback" appearance.

Kyphosis

An excessive forward rounding of the back, often called a hunchback, caused by structural spinal issues, poor posture, or weakening vertebrae.

What is the primary function of the thoracic cage?

To protect the heart and the lungs.

What structures compose the appendicular skeleton?

The pectoral limbs, pelvic limbs, pectoral girdle, and pelvic girdle.

How does the female pelvis differ from the male pelvis?

The female pelvis is lighter, wider, shallower, and has a broader angle between the pubic bones to adapt to reproductive fitness.

Subpubic angle (pubic arch)

Arch between the ischiums. A larger angle indicates female. The male counterpart is narrower

What are some examples of upper limbs?

Humerus (arm or brachium), Ulna and Radius (before the arm/antebrachium), Carpals(wrist), Metacarpal(palms), and phalanges(fingers)

What are some examples of lower limbs?

Femur(thigh), tibia and fibula(leg bones),patella(kneecap), tarsals(ankle), metatarsals(spans the foot), and phalanges(toes)

Sesamoid bone

A type of short bone that is embedded within a tendon, such as the patella.

Long bones

These are longer than wide, a shaft with two ends, mostly compact bone, and found in the limbs.

Flat bones

These consist of spongy bone embedded within parallel layers of thin compact bone.

Short bones

These bones are cube-like and mostly spongy.

Irregular bones

These bones are mostly spongy with a thin covering of compact bone, often found in complicated shapes.

Osteons

The structural units of compact bone, which consist of concentric rings called lamellae.

What is the function of the central (Haversian) canal in compact bone?

It serves as the core of the osteon and contains blood vessels and nerve tissue.

What is the role of perforating (Volkmann's) canals?

They connect the periosteum to the central and medullary cavities, providing blood supply and innervation.

Lacunae

Cavities containing osteocytes

Canaliculi

The channels that connect lacunae to each other and the central canal.

Trabeculae

The needle-like structures in spongy bone.

How is spongy bone organized compared to compact bone?

Spongy bone lacks osteons and is organized based on lines of stress, with trabeculae appearing less organized than compact bone structures.

How do trabeculae in spongy bone respond to physical forces?

They are arranged so that one side of the bone bears tension while the other withstands compression.

What are the initial cells involved in intramembranous ossification?

Mesenchymal cells, which differentiate into osteoblasts.

Osteoids

The substance that osteoblasts secrete during the early stages of bone formation, forming the bone matrix.

What is the function of the periosteum in bone development?

It serves as the interface between bone, blood vessels, tendons, and ligaments.

Endochondral ossification

The process of bone development from hyaline cartilage.

Periosteum

The connective tissue on the outside of bone that acts as the interface between bone, blood vessels, tendons, and ligaments during endochondral ossification.

How does endochondral ossification differ from intramembranous ossification?

Endochondral ossification uses a hyaline cartilage model as a pattern for bone construction.

What is the role of the periosteal bud in endochondral ossification?

It invades internal cavities, bringing blood vessels, nerve tissue, lymph tissue, osteoblasts, and osteoclasts.

What happens to the medullary cavity during endochondral ossification?

It forms as the bone collar thickens and the internal cartilage is broken down.

Fibrous joints

Joints that hold bones together with fibrous connective tissue.

Cartilaginous joints

Joints in which the bones are connected by cartilage.

Synchondrosis joints

Joints that join bones via hyaline cartilage, commonly found in the epiphyseal plates of growing children.

Symphyses joints

Joints located between the vertebrae, where bones are connected by fibrocartilage.

Synovial joints

Joints with a space or "synovial cavity" filled with lubricating synovial fluid.

Give an example of a planar synovial joint.

The joints of the carpal bones in the wrist.

What type of joint is the elbow joint?

A hinge joint.

What movement is permitted by a pivot joint in the neck?

Back and forth movement of the head.

Where are condyloid joints found in the human body?

The metacarpophalangeal joints in the fingers.

Which joint type is found in the thumb?

A saddle joint (carpometacarpal joint).

What is an example of a ball-and-socket joint?

The shoulder joint.

What are the three types of muscle tissue in the body?

Skeletal muscle, smooth muscle, and cardiac muscle.

Describe the appearance of smooth muscle cells.

They are short, tapered at each end, and contain one plump nucleus.

What are the structural characteristics of cardiac muscle cells?

They are branched, striated, short, and have one central nucleus.

Sarcolemma

The plasma membrane that surrounds a skeletal muscle cell.

Sarcomere

The region of a myofibril from one Z line to the next Z line.

Actin

This is what the thin filaments of sarcomeres are comprised of.

Myosin

This is what the thick filaments of sarcomeres are comprised of.

According to the sliding filament model, what happens to the Z lines during contraction?

The Z lines move closer together.

During muscle contraction, which band stays the same width?

The A band.

What triggers the cross-bridge muscle contraction cycle?

Calcium ions (Ca2+) binding to the actin active site.

What happens to the I band during sarcomere contraction?

It gets smaller.

Sarcoplasmic reticulum

This is where the calcium used for muscle contraction is released from.