The Structure Of The Humerus

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The Structure Of The Humerus
The Structure Of The Humerus

Video: The Structure Of The Humerus

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Video: Humerus Bone - Anatomy, Definition & Function - Human Anatomy | Kenhub 2023, February
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The structure of the humerus
The structure of the humerus

To perform the functions of support, movement and protection, our body has a system that includes bones, muscles, tendons and ligaments. All parts of it grow and develop in close interaction. Their structure and properties are studied by the science of anatomy. The humerus is part of the free upper limb and, along with the bones of the forearm and the girdle of the upper limbs - the scapula and clavicle - provides complex mechanical movements of the human hand. In this work, using the example of the humerus, we will study in detail the principles of the musculoskeletal system and find out how its structure is related to the functions performed.

Features of tubular bones

A triangular or cylindrical shape is characteristic of the components of the skeleton - tubular bones, in which such elements as the epiphyses (edges of the bone) and its body (diaphysis) are distinguished. Three layers - the periosteum, the actual bone and the endosteum - are part of the diaphysis of the humerus. The anatomy of the free upper limb is currently well understood. It is known that the epiphyses contain a cancellous substance, while the central section is represented by bony plates. They form a compact substance. Long tubular bones have this appearance: humerus, ulna, femur. The anatomy of the humerus, the photo of which is presented below, indicates that its shape best matches the formation of movable joints with the bones of the girdle of the upper limbs and forearm.

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How long bones develop

In the process of embryonic development, the humerus, together with the entire skeleton, is formed from the middle embryonic layer - the mesoderm. At the beginning of the fifth week of pregnancy, the fetus has mesenchymal areas called buds. They grow in length and take the shape of the humerus tubular bones, the ossification of which continues after the birth of the child. From above, the humerus is covered by the periosteum. This is a thin shell, consisting of connective tissue and having an extensive network of blood vessels and nerve endings that enter the bone itself and provide its nutrition and innervation. It is located along the entire length of the tubular bone and forms the first layer of the diaphysis. As established by the science of anatomy, the humerus, covered by the periosteum, contains fibers of an elastic protein - collagen, as well as special cells called osteoblasts and osteoclasts. They are grouped near the central channel of Havers. With age, it fills with yellow bone marrow.

Self-healing, repair and growth in the thickness of tubular bones in the human skeleton is carried out thanks to the periosteum. The anatomy of the humerus in the median part of the diaphysis is specific. There is a tuberous surface to which the superficial deltoid muscle joins. Together with the girdle of the upper limbs and the bones of the shoulder and forearm, it provides lifting and abduction of the elbows and arms up, back and in front of you.

The value of the epiphyses of tubular bones

The end parts of the tubular bone of the shoulder are called epiphyses, contain red bone marrow and are composed of a cancellous substance. Its cells produce blood corpuscles - platelets and erythrocytes. The epiphyses are covered by the periosteum and have bony plates and cords called trabeculae. They are located at an angle to each other and constitute the internal skeleton in the form of a system of cavities, which are filled with hematopoietic tissue. As determined by the anatomy, the structure of the humerus at the junction with the scapula and the bones of the forearm is quite complex. The articular surfaces of the humerus have proximal and distal ends. The head of the bone has a convex surface covered with hyaline cartilage and entering into the cavity of the scapula. A special cartilaginous formation of the scapular cavity - the glenoid lip - serves as a shock absorber that softens shock and shock during shoulder movement.The capsule of the shoulder joint is attached at one end to the scapula, and at the other to the head of the humerus, dropping down to its neck. It stabilizes the connection between the shoulder girdle and the free upper limb.

Bones

The anatomy of the human shoulder joint is complex. To provide mobility, the cavity is designed to be smaller, and the range of motion is provided by many tendons and muscles. The joint consists of two large bones - the humerus and scapula, several joints and many ligaments, tendons and muscles. The scapula is a flat, triangle-shaped bone. It is also important in building the articulation of the shoulder joint. The bone is found on the back of the torso and is easily felt under the skin. It has a glenoid cavity to which the humerus is attached. On the back of the scapula there is an axis dividing it in two, where the infraspinatus and supraspinatus muscles are located. On the scapula, there is another process called the coracoid that attaches the ligaments and muscles. Another bone, the clavicle, is tubular, with a curved shape.

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Features of the shoulder and elbow joints

As established by human anatomy, the humerus is part of not only the spherical shoulder joint, but also one more - the complex elbow. It should be noted that the shoulder joint is the most mobile in the human body. This is quite understandable, since the hand serves as the main instrument of labor operations, and its mobility is associated with adaptation to upright posture and release from participation in movement.

The elbow joint consists of three separate joints connected by a common joint capsule. The distal humerus connects to the ulna to form a blocky joint. At the same time, the head of the condyle of the humerus enters the fossa of the proximal end of the radius, forming the brachioradial movable joint.

Blood supply and innervation

The muscles of the shoulder girdle receive blood from the axillary artery and its branches. It crosses the armpit cavity and moves from the first rib to the bottom of the pectoralis major muscle, passing into the brachial artery. Vienna accompanies her. Innervation is realized through the nerves of the brachial plexus. It involves both spinal and those coming from the anterior branch of the thoracic nerve. The brachial plexus originates from the base of the neck, moves forward and downward, penetrating into the armpit cavity, goes under the collarbone, under the coracoid process of the scapula, giving off nerves there.

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Additional shoulder structures

The normal anatomy of the humerus includes the greater and lesser apophyses, the tubercles from which the ridges extend. They serve as the attachment point for the shoulder muscles. There is also a groove that serves as a receptacle for the biceps tendon. On the border with the body of the bone, the diaphysis, below the apophyses, there is a surgical neck. She is most vulnerable to traumatic shoulder injuries - dislocations and fractures. In the middle of the body of the bone there is a tuberous area to which the deltoid muscle is attached, and behind it there is a spiral-shaped groove into which the radial nerve is immersed. On the border of the epiphyses and the diaphysis, there is an area, the rapidly dividing cells of which cause the growth of the humerus in length.

Dysfunction of the humerus

The most common injury is a shoulder fracture from a fall or severe mechanical shock. The reason lies in the fact that the joint does not have real ligaments and is stabilized only by the muscular corset of the upper limb girdle and the auxiliary ligament, which looks like a bundle of collagen fibrils. Soft tissue lesions of the shoulder joint, such as tendonitis and capsulitis, are common. In the first case, the tendons of the supraspinatus, infraspinatus, and small round muscles are damaged. Another disease occurs as a result of inflammatory processes in the joint capsule of the shoulder.

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Pathologies are accompanied by tunnel pains in the arm and shoulder, limitation of the mobility of the shoulder joint when raising the arms up, placing them behind the back, abducting them to the sides. All these symptoms sharply reduce the performance and physical activity of a person.

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