Course Work Sample: Body Joints, Human Skeleton and Skeletal Muscle

The knee joint

The knee joint comprises of the ends of tibia and femur bones. The knee joint is surrounded by many ligaments and muscles that increase its stability. These ligaments consist of patella ligament, popliteal ligament, posterior and anterior cruciate ligaments. The joint is stabilized on the anterior side by the quadriceps, medial side by the Sartorius and the gracilis muscles, posterior by hamstrings, lateral side by fascia latae and gastrocnemius from underneath. The movements of the knee joint are: extension and flexion, medial and lateral rotations.

The ankle joint

The ankle joint consists of the talus and tibia bones. It has many ligaments to enable stability. The ankle movements include flexion when toes are up and extension with toes down. The muscles of the ankle joint include tibialis on the anterior responsible for dorsiflexion and supination, gastrocnemius on the posterior which is the primary ankle extensor.

The shoulder joint

The joint has glenoid fossa into which the head of the humerus fits. The shoulder joint is a ball and socket type of joint allowing movements like flexion, extension, abduction and circumduction.

Elbow joint

The bones in elbow joint include ulnar, radius and humerus. Bony configuration offers stability. The muscles in the elbow joint are the flexors which include biceps, pronator teres, brachioradialis, brachialis, wrist flexors, and extenders.

Spine and bone disorders

A: Lordosis

B: Kyphosis

C: Scoliosis

D: varus

Functions of the human skeleton

The human skeleton refers to the interior structure of the body comprised of many bones fused together. The human skeleton is divided into axial skeleton and appendicular skeleton. The axial skeleton is composed of the rib cage, skull, and vertebral column while the appendicular skeleton comprises of the shoulder girdle, pelvic girdle, and bones of the limbs. The human skeleton performs many vital functions which include; locomotion, maintenance of shape, protection of the internal organs, body support, blood cell production, endocrine regulation via the release of osteocalcin and storage of various essential minerals like calcium and iron (Chen and Ingber, 1999, p. 84-86).

Human skeleton enables locomotion and movement. The skeletal bones are held together by tendons, ligaments and skeletal muscles which help in movement. The musculoskeletal system empowers movement and stability. The shape of the bones and the types of joints allows for different kinds of movement coordinated by the nervous system. The human skeleton provides protection to the delicate internal organs by surrounding them with various bones. Bones are robust and flexible hence giving the skeleton the ability to absorb shock and take a blow without breaking (Taga, 1995). The protecting bones include the skull which protect the brain, the vertebrae which protects the spinal cord, the ribcage, sternum, and spine which protects lungs, heart and prominent blood vessels.

The human skeleton provides support to the body and helps keep the body organs in their right places. The pelvis, spine, and legs helps in the upright posture and support the entire body weight. The body cavities hold the internal organs, for example, the chest cavity contains the lungs and heart, skull houses the brain and the abdominal cavity encloses the digestive system. The human skeleton maintains body shape which changes as one grows determining height and size of feet and hands. The appropriate body shape enables essential body functions. Large bones contain red bone marrow which is involved in red blood cell production. Bone matrix stores calcium used in calcium metabolism while bone marrow stores ferritin involved in iron metabolism (Steele and Bramblett, 1988). Osteocalcin produced by bone cells which regulate blood sugar by increasing insulin production and also sensitivity.

Locomotion is the primary function of the human skeleton since it increases the chances of survival of people by allowing them to gather food, look for shelter and flee from dangerous situations. Locomotion also allows survival and continuity of the human race since it enables people to find the suitable mates. Therefore, I agree with the statement that locomotion is the primary function of the human skeleton.

The relationship between the skeletal bones to the skeletal functions

Protection - skull which protects the brain, ribcage, spine and sternum protects heart and lungs and vertebrae protects the spinal cord

Support - costal cartilage and the rib cage supports the lungs

Blood cell production - sternum, cranium, vertebrae, and pelvis

Bone matrix stores calcium

Skeleton images demonstrating the various functions of the human skeleton.

Most suitable joint for the following activities:

Extensive extension, flexion and rotation-pivot joint

Protection of soft tissue-fibrous joint

Flexion against force-hinge joint

List of the joints in order of movement range, starting with the most flexible.

Pivot joint

Ball and socket

Hinge joints

The classification of joints

Structural Class Structural Characteristics Types Type of Mobility

fibrous Short fibres

Long fibres

Peg in socket suture synarthrotic

syndesmosis amphiarthrotic

gomphosis synarthrotic

Cartilaginous Hyaline cartilage

fibrocartilage synchrondrosis

synarthrotic

symphysis

amphiarthrotic

synovial Have synovial fluid in cavity gliding Diarthrotic

hinge pivot Ball and socket saddle condyloid

A labeled rat dissection photograph is showing the different muscle types (Skeletal, muscular, and cardiac muscle).

Skeletal muscle adaptations and functions

Skeletal muscles are striated muscle tissue under the voluntary control of the somatic nervous system. They are attached to bones by tendons. They have myofibrils which contain actin and myosin responsible for contraction. Skeletal muscles have increased mitochondria and respiratory capacity (Lieber, 2002). They also have low utilization of oxygen and glucose hence suited for extensive exercises since they have the ability to withstand strenuous activities

Muscular muscle adaptations and function

Muscular tissue is smooth muscles which are non-nucleated, non-striated, whose work is to sustain contraction. Muscular muscles are found in the lining of the oesophagus, small intestines, blood vessels and urinary bladder providing support to these hollow organs. They are involuntary in nature involved in regulation of contraction and excitation-contraction coupling.

Cardiac muscle functions and adaptations

Cardiac muscles are involuntary and striated muscles found in the lining of the heart myocardium. The cardiac muscles have cardiomyocytes which are involved in contraction. Cardiac muscles get blood supply from coronary arteries. They have striations, t-tubules, and intercalated discs which help in transmission of impulses throughout the network hence enabling syncytium to cause contraction of the myocardium (Allen et al. 2001, p. 1906).

Strengths and weaknesses of agonist, antagonist and synergist muscle movement

Agonists are the prime movers; they are the muscles that are responsible for certain joint movements. Stabilizers, fixators, and neutralizers are also agonists. Agonists increase force in the direction of movement and produce concentric action. Therefore, agonist provides rotational movement at a joint via a production of force. Protagonists produce more force than its partners. The biceps brachii is the prime mover in elbow flexion.

Antagonists are muscles that oppose movement by producing a force that is opposite to a particular joint action. Antagonists are located on the opposite side of the agonist. The triceps which is the main extensor of the elbow joint is the primary antagonist of flexion. For an agonist to shorten, antagonist relaxes and reduce via reciprocal inhibition. However, antagonists also produce eccentric actions to stabilize a limb or reduce movement. For example, the hip extensors antagonize hip flexors bringing the femur forward in the running.

Synergistic muscle movement refers to situations where a group of muscles works together to perform a given motor task. A synergist is an agonist that is not the prime mover but helps in joint movement.

Muscles that enable elbow flexion, extension, pronation, and supination.

Activity Muscle

Flexion Brachialis, Biceps, brachii, brachioradialis. Flexor capri radialis, flexor capri ulnaris, palmaris longus and flexor digitorum superficialis

Extension Triceps Brachii, anconeus, extensor capri radialis longus, extensor digitorum

Pronation Pronator teres

Supination Supinator muscle

Energy pathways involved in muscle contraction

Muscle contraction or force exertion is due to adenosine triphosphate (ATP) molecule which is required for energy production. When an ATP molecule combines with water one of the phosphate is split apart hence producing energy. The breakdown of ATP results in the production of adenosine diphosphate (ADP). ADP is converted back to ATP through a series of chemical reactions to add the lost phosphate. The three energy pathways are ATP-PC system, glycolytic system, and the oxidative system. In the ATP-PC system, the stored ATP supplies the energy without the use of oxygen. The Glycolytic system provides glycogen that is broken down to form ATP through the process of glycolysis. The oxidative system produces ATP through the Krebs cycle, electron transport chain and beta-oxidation (Schunke et al. 2006).

References List

Allen, D.L., Harrison, B.C., Maass, A., Bell, M.L., Byrnes, W.C. and Leinwand, L.A., 2001. Cardiac and skeletal muscle adaptations to voluntary wheel running in the mouse. Journal of applied physiology, 90(5), pp.1900-1908.

Billotti, J.D., Billotti and Joseph D., 1996. Method for supporting body joints and brace therefor. U.S. Patent 5,527,267.

Chen, C.S. and Ingber, D.E., 1999. Tensegrity and mechanoregulation: from skeleton to cytoskeleton. Osteoarthritis and Cartilage, 7(1), pp.81-94.

Henneman, E. and Olson, C.B., 1965. Relations between structure and function in the design of skeletal muscles. Journal of Neurophysiology, 28(3), pp.581-598.

Lieber, R.L., 2002. Skeletal muscle structure, function, and plasticity. Lippincott Williams & Wilkins.

Panjabi, M.M., 1979. Centers and angles of rotation of body joints: a study of errors and optimization. Journal of biomechanics, 12(12), pp.911-920.

Paul, J.P., 1976. Force actions transmitted by joints in the human body. Proceedings of the Royal Society of London B: Biological Sciences, 192(1107), pp.163-172.

Schunke, M., Schulte, E., Schumacher, U., Ross, L.M. and Lamperti, E.D., 2006. Thieme atlas of anatomy: general anatomy and musculoskeletal system (Vol. 1). Stuttgart: Thieme.

Steele, D.G. and Bramblett, C.A., 1988. The anatomy and biology of the human skeleton. Texas A&M University Press.

Swynghedauw, B.E.R.N.A.R.D., 1986. Developmental and functional adaptation of contractile proteins in cardiac and skeletal muscles. Physiological reviews, 66(3), pp.710-771.

Taga, G., 1995. A model of the neuro-musculo-skeletal system for human locomotion. Biological cybernetics, 73(2), pp.97-111.

Zajac, F.E. and Gordon, M.E., 1989. Determining muscle's force and action in multi-articular movement. Exercise and sport sciences reviews, 17(1), pp.187-230.