Unit I. Anatomy

Text 1. The Skeletal System

The bones are the principal organs of support. They form a framework to which the skeletal muscles are attached.

Osseous tissue is connective tissue in which the intercellular substance is rendered hard by mineral salts, chiefly calcium phosphate and calcium carbonate. This inorganic matter constitutes about two thirds of the weight of bone. The organic matter consists of cells, blood vessels and cartilaginous substance. There are two forms of bony tissue: the cancellous, or spongy; and the dense, or compact. All bone is porous. The compact tissue has fewer spaces and is found on the exterior of a bone. Whereas the cancellous has larger cavities and is found in the interior of a bone. Bones have a hollow central canal, the medullary canal, which contains bone marrow. Blood cells are formed in the marrow tissue.

The adult skeleton consists of 206 bones.

The bones are classified according to their shape into long, short, flat, and irregular.

The surface of bones shows projections, or processes, and depressions, called fossae.

The head, or skull, rests upon the spinal column and is composed of the cranial and facial bones.

The axial skeleton consists of head and trunk.

The bones which form the trunk consist of the vertebrae, sternum, and ribs.

The bodies of the vertebrae, which are piled one upon another, form a strong, flexible column for the support of the cranium and trunk and provide articular surfaces for the attachment of the ribs. The thorax is a bony cage formed by the sternum and costal cartilages, the ribs, and the bodies of the thoracic vertebrae. The thorax supports the bones of the shoulder girdle and upper extremities and contains the principal organs of respiration and circulation. The sternum, or breastbone, is a flat, narrow bone, situated in the median line in the front of the chest. The ribs (costae) are situated 12 on each side of the thoracic cavity. They are elastic arches of bone.

The appendicular skeleton consists of the upper and lower extremities.

The two clavicles and the two scapulae form the shoulder girdle which serves to attach the bones of the upper extremities to the axial skeleton. The clavicle, or collarbone, is a long bone with a double curvature, which is placed horizontally at the upper and anterior part of the thorax. The scapula, or shoulder blade, is a large, triangular bone situated on the dorsal aspect of the thorax. The humerus, or arm bone, is the longest and largest bone of the upper extremity. The ulna, or elbow bone, is the largesr bone of the forearm and is placed at the medial side of the radius. The radius is placed on the lateral side of the ulna and is shorter and smaller than the ulna. The carpus, or wrist, is composed of eight small bones, united by ligaments. Metacarpus, or body of hand, if formed by five bones, numbered from the lateral side. The bones are curved longitudinally. The phalanges are the bones of the fingers, 14 in number in each hand, three for each finger and two for the thumb.

The two hipbones, which articulate with each other in front, form an arch called the pelvic girdle. This arch is completed behind by the sacrum and the coccyx, forming a rigid ring of bone called the pelvis. The pelvis attaches the lower extremities to the axial skeleton. The pelvis is strong and massively constructed. It is composed of four bones, the two hipbones forming the sides and front, the sacrum and coccyx completing it behind. The femur, or thighbone, is the longest bone in the body. The patella, or kneecap, is a small, flat bone placed in front of the knee joint. The tibia, or shinbone, lies at the front and medial side of the leg. The fibula is situated on the lateral side of the tibia, parallel with it. The seven tarsal bones (tarsus) differ from the carpal bones in being larger and more irregular. The largest and strongest of the tarsal bones is called the calcaneus, or heel bone; it serves to transmit the weight of the body to the ground. The metatarsus, or sole and instep of the foot, is formed by five bones which resemble the metacarpal bones of the hand. Phalanges of the foot resemble those in the hand, there being two in the great toe and three in each of the other toes.

Questions

1. Name the main parts of the body.

2. Name the parts of upper limb.

3. Name the parts of lower limb.

4. What is the function of skeletal system?

5. What kind of tissue is bone tissue?

6. What matters constitute the bone?

7. What forms of bony tissue are there? What is the difference between these forms?

8. What is there in the centre of the bone?

9. Where is bone marrow found? What is its function?

10. How many bones are there in the skeleton?

11. What are shapes of the bones?

12. What is there along the surface of the bone?

13. How do we call the bony box of the head?

14. What bones of the skull do you know?

15. What is the difference between the axial skeleton and the appendicular one?

16. What bones form the thorax?

17. What is the function of the vertebral column?

18. Where is sternum found?

19. How many ribs are there and where are they found?

20. What bones form the shoulder girdle and what does it serve to?

21. What are the bones of the upper extremity?

22. What two bones are placed in the forearm?

23. How do we call the bones of the fingers and of the toes? How many are they?

24. What bones construct the pelvic girdle? What does it serve to?

25. What bones of the lower extremity do you know?

26. What two bones are placed in the shin?

27. What bone of the foot serves to transmit body weight to the ground?

Something to Think about

1. Is the expression “dry as a bone” correct?

2. Do the bones have a protective function? Ground your answer.

3. What important minerals do bones store? What for are these minerals needed? (key-words: calcium, phosphorus)

4. What is the most important part of the skeleton? Why?

5. What two classes do naturalists divide all animals into? (Key-words: vertebrate, invertebrate)

6. What kinds of vertebrae do you know? (Key-words: cervical, thoracic, lumbar, sacral)

7. Why can we bend the wrist of the hand so freely?

8. What are fontanels? Where are they found? What do they serve to? (key-words: baby, skull, soft places, passage, narrow pelvic opening, birth)

9. What kinds of the joints do you know? (key-words: hinge, ball-and-socket, gliding, pivot)

10. What kind of movement does each of the joints allow? (key-words: back-and-forth, in all directions, sliding, turning)

11. Where is synovial fluid found? What is its function? (key-words: to surround, lubricant)

12. What kind of tissue does the baby’s skeleton consist of?

13. What is the difference between male and female skeleton? (key-words: pelvic region)

14. What connects muscles to bones? (key-word: tendon)

15. What attaches bones to joints? (key-word: ligament)

16. Why does our foot have the arch? (key-word: to spread weight evenly, to provide support, to absorb the shock, to protect vessels and nerves)

17. What is the longest bone of the body?

18. Give the English equivalents to the following Latin words: mandible, extremity, maxilla, clavicle, sternum, cranium.

Text 2. The Muscular System

Muscles are the “engines” of the body; they provide the power for movement.

Special characteristics of muscle tissue are irritability, contractility, extensibility, and elasticity. Irritability is the ability of muscle to receive stimuli and respond to them. Contractility is the ability of muscle to become shorter and thicker after being stimulated. Extensibility is the ability of muscle to stretch. Elasticity is the ability of muscle to return to its original size and form.

Muscle tissue is composed of elongated cells termed fibers. The fibers lie closely packed, forming primary bundles, or fasciculi. Loose connective tissue surrounds the bundles and forms the covering for the entire muscle trunk, which is called fascia. A typical muscle consists of a body and two extremities. Tendons and aponeuroses attach muscles to bones. A tendon, a dense white cord, is exceedingly strong, inextensible, and at the same time flexible. A flattened tendon is referred to as aponeurosis.

Muscular tissue may be classified according to its structure as striated, smooth, and indistinctly striated. According to its location it may be classified as skeletal, visceral, and cardiac.

Striated muscular tissue is called striated because of the parallel cross stripes. It is called skeletal because it forms the muscles which are attached to the skeleton. It is called voluntary because the movements accomplished are under conscious control. The function of skeletal muscle is to operate the bones of the body, thereby producing motion.

Smooth muscular tissue does not exhibit cross stripes. It is called visceral because it forms the muscular portion of the visceral organs. It is called involuntary because it is not under nerve control as is skeletal muscle. The function of smooth muscle cells is to produce changes in shape and size of visceral organs. An example is peristalsis of the alimentary canal.

Cardiac muscle tissue forms the heart. The myofibrils are similar to those in skeletal muscle, but transverse striations are less distinct. The cardiac muscle cells fit tightly together.

Muscles bear two names, one Latin and the other English, e.g., obliquus externus abdominis and external abdominal oblique. Frequently a muscle has no well-known English name, e.g., levatores costarum. Sometimes the English name is the one that is best known, e.g., deltoid instead of deltoideus.

Tone is a property of muscle to maintain a steady, partial contraction varying in degree. Physiologically the tone is due to nerve impulses. During sleep, tone is at a minimum. By means of tonic contraction in skeletal muscles, posture is maintained for long periods. It also functions in the maintenance of pressure upon the contents of the abdominal cavity as well as of normal blood pressure in the arterial walls. Both the rapidity and the smoothness of movement depend on tone.