Summary of Chapter 6.2 Locomotion - Key Points The muscular and skeletal systems sustain the body and allow it to move. To demonstrate how these two organ systems cooperate to create movement, we will focus on the relationship between the human skeletal and muscular systems, with references to other animal skeletal and muscular systems. The human skeleton is an endoskeleton with 206 bones in an adult. The skeleton has five primary functions: it supports the body, stores minerals and fats, produces blood cells, protects internal organs, and allows mobility. The axial skeleton, which includes the skull bones, ossicles of the middle ear, hyoid bone of the neck, vertebral column, and thoracic cage, serves as the body's central axis (rib cage). The skull bones protect the brain and support the structures of the face. The skull is made up of cranial and facial bones. The cranial bones create the cranial cavity, which encloses the brain and acts as a place for head and neck muscles to connect. They are securely joined by connective tissue in adults, and neighbouring bones do not move. The auditory ossicles of the middle ear convey vibrations from the air to the fluid-filled cochlea. Facial bones serve as attachment places for facial muscles as well as cavities for sense organs (eyes, mouth, and nose). The hyoid bone is located at the front of the neck, beneath the jaw. It serves as a moveable basis for the tongue and is linked to jaw, larynx, and tongue muscles. The vertebral column, also known as the spinal column, covers and protects the spinal cord, supports the head, and serves as an attachment point for ribs and back and neck muscles. It is made up of 26 bones: 24 vertebrae, a sacrum, and a coccyx. From the second cervical vertebrae to the sacrum, cartilaginous intervertebral discs create slightly moveable joints that absorb shock to allow for activities like walking or running. The ribs, sternum, thoracic vertebrae, and costal cartilages make up the thoracic cage, commonly known as the rib cage. The thoracic cage encloses and protects the thoracic cavity's organs, including the heart and lungs. It also supports the shoulder girdles and upper limbs and acts as an attachment point for the diaphragm, back, chest, neck, and shoulder muscles. Breathing is enabled through changes in the volume of the thorax. The sternum, often known as the breastbone, is a long, flat bone found in the front of the chest. It, like the skull, is produced in the embryo from numerous bones that merge in the adult. The ribs are 12 pairs of long, curved bones that join to the thoracic vertebrae and bend forward to form the ribcage. Costal cartilages attach the anterior ends of the majority of ribs to the sternum. The appendicular skeleton is made up of the upper and lower limb bones. The pectoral, or shoulder girdle, which connects the upper limbs to the body, and the pelvic girdle, which connects the lower limbs to the body, are also included. The pectoral girdle bones carry force generated by upper-limb muscles to the thorax. It is made up of the clavicles (or collarbones) in the front and the scapulae (or shoulder blades) in the back. The upper limb includes the bones of the arm (shoulder to elbow), forearm, and hand. The humerus is the upper limb's biggest and longest bone. It connects to the shoulder and the forearm at the elbow. The forearm is made up of two bones that go from the elbow to the wrist. The pelvic girdle connects to the appendicular skeleton's lower limbs. The pelvic girdle is tightly connected to the axial skeleton by strong ligaments because it bears the weight of the body and is responsible for movement. The pelvic girdle is mostly made up of two big hip bones. The lower limb is made up of the thigh, leg, and foot. Lower limb bones are thicker and stronger than upper limb bones to carry the total weight of the body as well as the stresses of movement. The femur, often known as the thighbone, is the longest, heaviest, and most powerful bone in the body. The hip joint is formed by the femur and pelvis. A joint, or articulation, is the place where two or more bones come together. Joints are responsible for movement, such as limb movement, and stability, such as the stability seen in skull bones. Joints can be classified in two ways: based on their structure or based on their function. Joints are classified as fibrous, cartilaginous, or synovial based on the material that makes up the joint and the presence or absence of a cavity in the joint. Fibrous connective tissue holds the bones of fibrous joints together. Cartilaginous joints have a limited range of motion. The only joints with a gap between the neighbouring bones are synovial joints. This region is known as the joint cavity, and it is filled with fluid. The fluid lubricates the joint, decreasing friction and allowing for better mobility. Synovial joints have the highest range of motion of any joint type. Synovial joints include the knees, elbows, and shoulders. Synovial joints allow for a wide range of mobility, which results in a variety of motions. Flexion is demonstrated by moving the forearm upward at the elbow. Rotation is demonstrated by the movement of the head when saying "no." Humans can only move on two limbs on land or swim with all four limbs on water. Birds are great swimmers and flyers. Some birds, however, are unable to move in both the air and the water.