Skeletal Anatomy

16.5 Musculoskeletal System

The Muscular and Skeletal system

Provide support for the body and allow movement.

Skeletal System

The human skeleton is an endoskeleton consisting of 206 bones in the average adult human body, it develops within the body.

Endoskeleton

An internal skeleton composed of the axial and appendicular skeleton

Exoskeleton

An outer shell that supports and portects the skeleton for animals such as insects.

The main functions of the skeletal system

Provides support to the body, stores minerals and lipids, produces blood cells, protects internal organs, and allows for movement to happen.

Axial Skeleton

Forms the axis of the body, ossicles of the middle ear, hyoid bone of the throat vertebral column and thoracic cage (rib cage).

Skull

Supports the structure of the face and protects the brain, consisting of cranial bones and facial bones.

Auditory ossicles (Middle ear)

Transmits sounds from the air as vibrations to the fluid-filled cochlea. Consisting of 2 malleus (hammer) bones, two incus (anvil) bones, and two stapes (stirrups), one on each side.

Hyoid bone

Lies below the mandible (jaw) in the front of the neck. It acts as a movable base for the tongue and is connected to muscles of the jaw, larynx, and tongue.

Vertebal column (spinal cord)

Surrounds and protects the spinal cord, and acts as an attachment point for ribs and muscles of the back and neck. Consisting of 26 bones: the 24 vertebrae, the sacrum, and the coccyx. (Approx. 70 cm or 28 inches in adults and curved, seen from a side view.)

Thoracic cage

Encloses and protects the organs of the thoracic cavity including the heart and lungs. As well provide support for the shoulder girdles and upper limbs and serves as the attachment point for the diaphragm, muscles of the back, chest, neck, and shoulders.

Appendicular skeleton

Composed of the bones of the upper and lower limbs. It also includes the pectoral, or shoulder girdle, which attaches the upper limbs to the body, and the pelvic girdle, which attaches the lower limbs to the body.

Pectoral girdle

Transfer force generated by muscles acting on the upper limb to the thorax. It consists of the clavicles (or collarbones) in the anterior, and the scapulae (or shoulder blades) in the posterior.

Pelvic girdle

Attaches to the lower limbs of the axial skeleton. It is responsible for bearing the weight of the body and for locomotion, securely attached to the axial skeleton by strong ligaments. Mainly composed of two large hip bones.

Joint

The point where 2 or more bones meet, responsible for movements.

Fibrous joints

Cartilaginous joints

Joints in which the bones are connected by cartilage. Allows for little movement.

Synovial joints

The only joints that have a space between the adjoining bones. The space is called a joint cavity and filled with fluid, the fluid reduces friction between joints and allows for greater movements.

Flexion

Bending occurs when the angle between the bones decreases.

Extension

The opposite of flexion in that angle between the bones of the joint increases.

Muscles

Allows for movement, containing 3 types of muscle tissues: skeletal muscle, cardiac muscle, and smoothh muscle. 

Skeletal muscle tissue

Forms skeletal muscles, which attaches to bones and sometimes the skin and control locomotion and any other movement that can be consciously controlled.

Smooth muscle tissue

Occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as in the respiratory tract and blood vessels. Has no striations, is not under voluntary control, and is called involuntary muscle, has a single nucleus.

Cardiac muscle tissue

Only found in the heart. The contractions pump blood throughout the body and maintain blood pressure.

Myofibrils

Long cylindrical structures that lie parallel to the muscle fiber. Runs the entire length of the muscle fiber. Attaching to the plasma membrane called..

Sacrolemma

A plasma membrane, at their ends, so that as myofibrils shorten, the entire muscle cell contracts.

Myofilaments

Small structures composing Myofibrils, 2 main types are thick and thin filaments.

Sarcomere

A structure where the thick and thin filaments alternate with each other. A unit of contraction in the muscle cell.