Support and Movement

• Chapter 16 discusses support and movement in living organisms.
• Focus is given to the components, structure, and function of the human musculoskeletal system.

Human Skeleton

• The vertebrate skeleton is composed of cartilage or bone, providing an internal supporting framework.
• It is necessary to uphold and sustain the body against gravity and other external forces.

Cartilage

• Cartilage is a connective tissue made of chondrocytes and a matrix of type II collagen.
• Unlike other connective tissues, cartilage lacks blood vessels and receives nutrients via diffusion.
• Hyaline, elastic, and fibrocartilage are the three types of cartilage tissue in the human body.

Bone

• Bones provide structural support, protect internal organs and act as a storage place for minerals.
• Bone is a rigid connective tissue that forms the endoskeleton of vertebrates.
• Bone resists compression and bending.
• Bone matrix consists of about 65% inorganic matter (calcium phosphate, carbonate) and 35% organic substances (protein, collagen).

Bone Structure

• Bone is surrounded by a membrane called the periosteum.
• Numerous round canals, the Haversian Canals, are found in bone.
• Concentrically arranged boney plates called Haversian lamellae surround each canal.
• Calcified matrix with collagen fibers are embedded in the Haversian lamellae.
• Lacunae, containing bone cells or osteocytes, are spaces between adjacent lamellae.
• Fine fibers or canaliculi radiate from the lacunae in all directions.
• The Haversian system includes the Haversian canal with surrounding lamellae, lacunae, and canaliculi.

Bone Marrow

• Some bones contain soft tissue called bone marrow.
• Red bone marrow, found in spongy bone, produces red blood cells, platelets, and white blood cells.
• Yellow bone marrow, found in the shafts of long bones, serves as an energy reserve and consists mostly of fat cells.

Bone Cells

• Osteoblasts, osteocytes, and osteoclasts are the three types of specialized cells in human bones.
• Osteoblasts make new bone cells and are responsible for bone growth.
• Osteocytes regulate mineral homeostasis.
• Osteoclasts dissolve minerals in bone matrix.

Main Divisions of the Human Skeleton

• The human skeleton is divided into the axial and appendicular skeletons.
• At birth, the skeleton consists of about 350 bones, which fuse to 206 in adults.
• The axial skeleton is the basic framework of the body.
• The appendicular skeleton includes the extremities.

Axial Skeleton

• The axial skeleton includes the skull, vertebrae, and ribs.

Skull

• The skull is a bony structure that supports the face.
• The skull forms a protective casing cavity for the brain.
• The bones of the skull are joined by sutures (fibrous joints).
• There are cranial and facial bones in the skull.

Cranial Bones

• The cranium consists of 8 bones: frontal, occipital, sphenoid, ethmoid, 2 parietal, and 2 temporal bones.

Facial Bones

• The 14 facial bones are: Zygomatic (2), Lacrimal (2), Nasal (2), Inferior nasal conchae (2), Palatine (2), Maxilla (2), Vomer, Mandible (jaw).

Middle Ear Bones

• The middle ear contains the auditory ossicles: malleus, incus, and stapes.

Neck Bone

• The hyoid bone is a ‘U’ shaped structure.
• It is located in the anterior neck.

Vertebral Column

• The vertebral column forms a flexible rod.
• The vertebral column extends through the length of the trunk.
• It houses and protects the spinal cord.
• Humans have 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal vertebrae.

Ribs

• Humans have 12 pairs of ribs that articulate with the thoracic vertebrae, forming a protective cage.
• The first seven pairs are connected to the sternum as true ribs.
• The next three pairs are indirectly connected to the sternum as false ribs.
• The lower two pairs are not attached in front and are called "floating ribs".

Appendicular Skeleton

• Forelimbs, pectoral girdle, pelvic girdle, and the hind limbs make up the appendicular skeleton.

Pectoral Girdle

• The pectoral girdle consists of a ventral coracoid, scapula, and clavicle.

Forelimbs

• The forelimbs consist of a humerus, radius, ulna, carpels, metacarpels, and phalanges.

Pelvic Girdle

• The pelvic girdle attaches to the vertebral column.
• The pelvic girdle is made of two coxal bones formed by the fusion of the three bones; ischium, illium and pubis.

Hind Limbs

• Each hind limb consists of a thigh, shank, ankle, and foot.
• In the hind limb there is a single femur in the thigh, tibia and fibula in the shank, and metatarsals and phalanges in the foot.

Joints

• Joints or articulations are sites where two or more bones meet.
• Joints provide mobility and hold the skeletal parts.
• Fibrous, cartilaginous, and synovial joints are the three types of joints.
• Structural classification of joints is based on the material binding the bones together and whether or not a joint cavity is present.

Fibrous Joints

• In fibrous joints, fibrous connective tissue holds the bones firmly.
• Fibrous joints generally are immoveable and provide strength and support.

Cartilaginous Joints

• Cartilaginous joints cartilage entirely connects them.
• These joints allow slight movement and are found between vertebrae.

Synovial Joints

• Synovial joints are separated by a fluid-containing joint cavity (synovial cavity).
• This arrangement allows freedom of movement so they are freely movable.
• Ligaments reinforce and strengthen synovial joints.
• Hinge and ball-and-socket joints are the two major categories of synovial joints.

Hinge Joints

• A cylindrical projection of one bone fits into a trough-shaped surface on another in Hinge joints.
• Hinge joints permit flexion and extension.
• Elbow and knee joints are examples

Ball-and-Socket Joints

• The spherical head of one bone articulates with the cuplike socket of another in ball-and-socket joints.
• The shoulder and hip joints are the most freely moving synovial joints.

Disorders of the Skeleton

• Disorders of skeleton can result in reduced movement or complete immobility.
• Deformities may be genetic, hormonal, or due to nutrient deficiency.

Disc Slip

• Rupture or slippage of a vertebral disc.
• The intervertebral discs acts as a shock absorber.
• The leaking jelly-like substance places pressure on the spinal cord.

Spondylosis

• Degenerative disorder that may cause loss of normal spinal structure and function.
• Aging is the primary cause.

Sciatica

• Pain, weakness, numbness, or tingling in the leg.
• Sciatica is caused by injury to or pressure on the sciatic nerve.

Sprain

• A sprain is where the ligaments are stretched or torn.

Muscles

• Muscle tissue is a specialized tissue of mesodermal origin.
• Three types of muscles exist: skeletal, cardiac, and smooth.

Skeletal Muscles

• Skeletal muscles are attached to and cover the bony skeleton.
• Obvious stripes called striations are found within muscles connected to the skeleton.
• The muscles are under voluntary control.
• Skeletal muscles are involved in locomotory actions and changes of body postures.

Cardiac Muscles

• Cardiac muscles are only in the heart. They make up the bulk of the heart walls.
• Skeletal muscle cells, also cardiac muscle cells are striated, but are involuntary and have single nucleus.
• Cardiac muscles contract rhythmically.
• Atria and ventricles contract in the heart to pump blood.

Smooth Muscles

• Smooth muscles are in the walls of hollow visceral organs, such as the stomach.
• No striations are present so they are called smooth.
• Smooth muscles are not subject to voluntary control.
• Substances are controlled through hollow organs by smooth muscle.

Structure of Skeletal Muscles

• Muscle bundle makes up the skeletal muscle which is made up of large elongated cells.
• Muscle fibres are the huge elongated cells that make up the fibers.
• The sarcoplasm, or cytoplasm, of each fiber is a semi-fluid matrix.

Muscle Contraction

• Contractility is a fundamental characteristic of living substance.
• Muscle fibre contraction is described by the sliding filament hypothesis.

Muscle Fibre Relaxation

• Sarcoplasmic reticulum re-accumulates the calcium ions by active transport.
• The myosin heads and actin filaments cannot bind.

Antagonistic Muscles

• When a bone is moved by a given muscle.
• Antagonistic muscles involves the bone being returned by the other muscle that opposes the movement.