Unit 4: Homework Submit Assignment Due Sunday by 11:59pm Points 14 Submitting a

Question

Unit 4: Homework Submit Assignment Due Sunday by 11:59pm Points 14 Submitting a file upload Post to Submit Assignment by Sunday night. 1. Explain why people confined to wheelchairs because of paralyzed lower limbs have thin, weak bones in their thighs and legs. 2. The major function of the pectoral girdle is mobility. What is the major function of the pelvic girdle? These two girdles attach differently to the axial skeleton. This form of attachment is related to their particular function in the body. How do these attachments differ? 3. Name two specific examples of each: hinge joint, plane joint, ball- and-socket joint. 4. Describe the correlation between the type of joint and its range of motion. Explaining the reasons for this relationship. The following rubric will be used to score your homework postings. Question 1 Clear explanation provided Question 2 Major function identified and explanation of differences uestion Two examples of each provided 0-2 pts 5 pts 0-3 pts

Explanation / Answer

, 1. Formation of new bone and resorption of existing bone occurs to meet the body's needs. Healthy bones adapt to the mechanical forces they encounter in the body. When the muscle moves, the force applied by the muscle on the bone helps blood flow and mineral deposition on the bone. This helps to build and strengthen the bone. People confined to wheelchairs cannot move their legs. There is no activity for the muscles on their thighs and legs. When these muscles are not used, the bones begin to lose minerals, start thinning and weaken.

2. The pelvic girdle connects the bones of the lower limbs to the axial skeleton. The bones of the pelvic girdle are strong and largely immobile to form a weight-bearing structure It provides a strong foundation for the upper body that rests on the mobile lower limbs.

The scapula or shoulder blade that is a part of the pectoral girdle does not make a visible connection or joint with the axial skeleton. It is attached to the ribs, sternum, and vertebrae by muscles. This allows the scapula to be very mobile which is essential for the movement of the upper limbs. The hip bone of the pelvic girdle is joined to the sacrum which is part of the axial skeleton through the sacroiliac joint.

3. Hinge joint: Knee joint, Elbow joint

Plane joint: Joints between carpal bones of the wrist, between carpals and metacarpals of the palm

Ball & Socket joint: Shoulder and hip joints

4. Joints can be classified in several ways

Functional classification is based on how much movement they allow. A joint that permits no movement is called synarthrosis, that allows a slight amount of movement at the joint is known as amphiarthrosis and those that are freely movable and have the highest range of movement are known as diarthrosis.

Structural classification is based on the type of material present in the joint. Based on this joints can be classified as fibrous, cartilaginous or synovial joints.

The most common type is the synovial joint and it has different classes- gliding joint, hinge joint, saddle joint, ball & socket joint.

Gliding joints allow bones to glide past each other in any direction. They are found where bones meet as flat surfaces. Hinge joints limit the movement of bones in only in one direction so that the angle between the bones can increase or decrease at the joint. Saddle joints allow 360 degrees motion by allowing the bones to pivot along two axes. Ball & Socket joints have the freest range of motion in the body and allow the bones to move in a full circle and rotate around their axis.

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