Angiogenesis

Angiogenesis is the natural biological process by which new blood vessels are formed. It is a normal process during the development of the fetus and the growth of the body from childhood to adulthood as the need for more blood supply arises. The development of new arterial branches and veins also happens during reparation and replacement of damaged tissue and during the formation of malignant tumor.

Angiogenesis also takes place in the cerebral cortex when new synaptic links are established among neurons during the process of learning new skills, be it intellectual or motor. When there is new synapses in the brain, new support cells, such as oligodendrocytes and astrocytes are formed and the need for more blood supply arises; these cells are the support cells of neuron axons.

Angiogenesis is caused by the development of vascular endothelial cells within a parenchymal tissue as a need to improve the supply of oxygen-rich blood to new areas which are the result of natural growth or development. For example, when an athlete develops muscles when he lifts weights, there is the need for more blood supply for more muscular mass. These squamous endothelial cells multiplication is due to the endothelial growth factor, which is a protein. Endothelial cells make up the single wall of capillaries and they also form the inner wall of arterioles and arteries (tunica intima). As endothelial cells divide, they in turn secrete more growth factor, which stimulate the growth of smooth muscle cells as well. Smooth muscle cells constitute the middle layer of artery wall.

Angiogenesis is very important in the recovery of heart muscle damage after a heart attack caused by coronary artery occlusion. Since the formation of new blood vessels creates important anastomosis (vascular connections/bridges) that prevent damage when an artery or arteriole get occluded or burst. Thus, it is an important biological tool to repair tissue but it also protects both the myocardium and the brain tissue from damage as anastomosis ensure permanent blood supply.

Human Clavicle

The human clavicle is what we commonly call the collarbone. It is a slender, tubular and S-shaped bone. It has a lateral and a medial end. The lateral tip is the acromial end, which articulates with the acromium of scapula. The medial extremity, on the other hand, is called the sternal end, which articulates with the manubrium sterni of sternum.

The acromial end of human clavicle is wider but slightly thinner than the sternal end, which has a sternal articular facet. Looking at it from above, the sternal half of the collarbone makes a forward curve. The inferior surface of the sternal end bears the costal tuberosity, which serves as the site of attachment for the costoclavicular ligament. The inferolateral surface of the lateral end features the acromial articular facet.

The acromial end also bears the conoid tubercle and the trapezoid line, which give attachment to the conoid and trapezoid parts of the coracoclavicular ligament.

Below, the superior and inferior view of right human collarbone.

 

 

Thoracic Vertebrae

The thoracic vertebrae are twelve in number. Compared to the cervical vertebrae, they are higher and thicker and they lack the transverse foramen in their transverse process. As the spinal column runs down towards the lumbar vertebrae, their bodies gradually increase in size as they get thicker. There is a concavity on the inferior and superior surface at the base of the vertebral arches; it is the vertebral notch; thus, the two adjacent vertebrae notches form the intervertebral foramen for the spinal nerve roots.

The arches of the thoracic vertebrae form an almost circular vertebral foramina, which is the orifice through which the spinal cord runs; however, it is smaller in diameter than the cervical vertebrae foramina. The transverse process of the thoracic vertebrae extends laterally and obliquely backwards, bearing a small costal facet which articulates with the tubercle of rib. Their spinous processes are long, three-sided, and pointing downwards. Those of the middle thoracic vertebrae fit one over the other, like tiles.

The posterolateral surface of each one of the thoracic verterae bears two facets; the superior costal facet and the inferior costal facet. The inferior facet of one vertebra joins the superior facet of the adjacent distal vertebra (the one below) to give shape to a complete articular facet, which is the site of articulation with the head of the rib. However, the body of the first thoracic vertebra is an exception, for it has a complete articular facet by itself for articulation with the head of the first rib on the superior part of the posterolateral surface, as well as a semifacet for articulation with the head of the second rib on the inferior part.

The tenth vertebra features one superior semifacet on the superior part of the body. Meanwhile, the bodies of the eleventh and twelfth vertebra each bears only one complete costal facet in the middle of each lateral surface.

Below, lateral view of a thoracic vertebra. Every part is labeled

Below, the eighth thoracic vertebra, superior view

 

Human Scapula

The human scapula, or shoulder blade, is a flat bone of the shoulder girdle region. It lies between the muscles of the back, from the second to the seventh rib. Since it is triangular in shape, three borders and three angles are distinguished in it. The anterior surface is concave and it is called the subscapular fossa, which is occupied by the subscapular muscle.

The posterior or dorsal surface of scapula is divided into two parts by the spine of the scapula. The upper part, which is much smaller, is located immediately above the spine and it is called the supraspinous fossa. The lower larger part occupies the rest of the dorsal surface. They are the site of origin of the supraspinatus and infraspinatus muscle, respectively. Meanwhile, the spine of the scapula, as it extends laterally and upwardly, projects a thick, beak-like protrusion called the acromion. The acromion articulates with the clavicle (collarbone).

The upper border of scapula is thin and features the suprascapular notch. This notch is bridged by the superior transverse ligament of scapula, forming an opening through which the suprascapular nerve goes through. Next to it is the coracoid process, which is a bony protrusion that juts out upwards and then laterally. The coracoid process is the site of origin of two arm muscles; the coracobrachialis and the short head of biceps brachii muscle. The rest of the upper border of scapula is thinner, ending in the superior medial angle, which is also thin.

The superior lateral angle is thick. Right below this angle, the scapula bears a thickened concave surface; this is the glenoid cavity, for articulation with the articular surface of the head of humerus. This union is the shoulder joint. The supraglenoid tubercle is located above the superior margin of the glenoid cavity, while the infraglenoid tubercle is found right below the glenoid cavity. The supraglenoid tubercle is the site of attachment for the tendon of long head of the biceps brachii muscle, while the infraglenoid tubercle is site of attachment of the long tendon of triceps.

Below, anterior view of human scapula.

 

Below, dorsal view of shoulder blade.

Shoulder Girdle Bones

The shoulder girdle bones are three in number. The scapula, the clavicle (collarbone), and the humerus. They meet at the superior, lateral corner of trunk to form two joints: the shoulder joint and the acromioclavicular joint; the former is the union of the head of humerus with the superior lateral corner of scapula; the latter is the union of collarbone with the acromion of scapula. All three bones are united at this angle by strong ligaments and cartilage.

The humerus and clavicle are longitudinal bones, but the scapula is rather flat and irregular in shape. It projects laterally and upwardly two longitudinal bony protrusions; the acromion and the coracoid process, which resembles a crow's beak. The short head of biceps brachii, the strongest muscle of arm, and the coracobrachialis muscle are attached to the coracoid process.

But the scapula also features on its superior lateral aspect a concave depression; it is the glenoid cavity, into which the head of humerus fits. This is called the shoulder joint. Meanwhile, the lateral end of the clavicle articulates with the acromion of scapula; this is called the acromioclavicular joint.

Below, a shoulder girdle radiograph shows the bones of this portion of the human body. 1- first rib; 2- medial border of scapula; 3- intercostal space; 4- lateral border of scapula; 5- scapula; 6- glenoid cavity of scapula; 7- humerus; 8- greater tuberosity of humerus; 9- anatomical neck; 10- acromion; 11- coracoid process of scapula; 12- clavicle; 13- spine of scapula; 14- superior border of scapula; 15- head of humerus; 16- surgical head.

 

Human Pelvis

The human pelvis is the wide bone structure at the lower end of the trunk. It supports and contains the last portion of the digestive tract and the urogenital system. Large muscles of the thigh and hip are anchored to it. It articulates with the head of femur at the acetabulum cavity. 

The shape and dimensions of pelvis depend on the sexual differences and individual body size. The average width of female pelvis is 27 cm, while it is 24 cm in the male; this is called the intercristal diameter, extending from the lateral iliac crest of one hip bone to the other of the opposite side. The frontoposterior diameter and pelvic cavity are also wider in female by one and half centimeter.

Anatomical Description

The human pelvis is composed of the two hip bones, the sacrum, and the coccyx. They are all joined together into one anatomical unit by cartilage, ligaments, and joints. The widest part of each one of the hip bones is called the ilium. The upper edge of the ilium is the iliac crest, which runs from back to the frontolateral portion of the pelvis, curving around the side. On the lateral side, the hip bone features a concave cavity; the acetabulum, in which the head of femur fits snugly.

The foremost frontal portion of the hip bone is very narrow compared to the rest and is below the iliac crest; it is called the pubis. The pubis of each hip bone is joined to the one of the opposite side at a medial line by the pubic symphysis, which is a fixed joint made of cartilage. Meanwhile, the bone arch at the bottom and rear portion of the hip bone is called the ischium, which forms an opening referred to as the foramen obturatum. Powerful muscles of the medial side of thigh are attached to the ischium, such as the adductor magnus.

As a whole, the human pelvis can be divided into the greater pelvis and the lesser pelvis. The greater pelvis is bounded on the sides by the wing of the ilium, and posteriorly by the lower lumbar vertebra and the base of the sacrum. Its inferior boundary consists of the crest of the pubis and the frontolateral portion of crest of ilium; this inferior boundary is called the arcuate line of the pelvis.

The lesser pelvis, on the other hand, is located below the arcuate line. Its lateral walls are formed by the lower part of the bodies of the ilia and ischia, the posterior wall by the sacrum and coccyx, and the anterior wall by the two pubic bones.

Below, the female human pelvis, with its different parts labeled. It is wider than the male's.

Coccyx

The coccyx is the distal end of the spinal column in human beings. It is the rudimentary tail of the mammals. Being the continuation of the sacrum, it curves inwardly as it tapers to a point. It is composed of four or five coccygeal vertebrae, which fuse together into one bone structure in adults.

The coccyx has the shape of an inverted pyramid, with its base facing upwards and the apex downwards. The vertebrae that form it are deprived of transverse process and spinous process. They have only bodies. On each side of the first coccygeal vertebra are the remnants of the superior articular processes in the form of small projections, which are called the coccygeal cornua. These extend upward to articulate with the sacral cornua.

The superior surface of the coccyx has a slight concave area, which articulates with the apex of the sacrum by means of the sacrococcygeal joint.

Below, anterior (A) and posterior (B) view of the coccyx.

 

Cervical Vertebrae

The cervical vertebrae are the seven uppermost bone pieces of the vertebral column. They are located immediately below the skull, with each one of them being separated from the other by a disc of cartilage. They are: C1, C2, C3, C4, C5, C6, C7. The most superior one is called atlas (C1), connecting the base of the skull with the vertebral column. The second cervical vertebra, on the other hand, is called the axis (C2).

From C3 to C7, a cervical vertebra consists of an anterior body; a posterior spinous process, which juts out backwards, ending in a point; two lateral transverse processes; and two inferior articular processes. The vertebral foramen, through which the spinal cord runs, is bounded and contained by these bone processes. The lateral transverse processes of the cervical vertebrae also contain a smaller opening called transverse foramen, through which the vertebral arteries runs up into the head. The distal cervical vertebra articulates with the proximal thoracic vertebra, which is taller and thicker.

Below, a radiograph of the neck region (lateral view). It shows the seven cervical vertebrae. 1- atlas; 2- the axis; 3- transverse process; 4- spinous process; 5- articular process.

Atlas and axis (first and second vertebrae) articulating together (posterior view)

 

Second cervical vertebra’s lateral view

Second Cervical Vertebra

The axis is the second cervical vertebra. It has an odontoid process, or dens, which is a tooth-like protrusion, lined with cartilage, which articulates with the atlas on top. The atlas, together with the skull turns about the odontoid process as if it were an axis, hence the name. The anterior aspect of the odontoid process bears an anterior articular facet for articulation with the facet for the dens of the first cervical vertebra. Meanwhile, the posterior side of the axis dens has a posterior articular facet, on which the transverse ligament of the atlas adjoin.

At the base of the transverse process on both lateral aspects, the second cervical vertebra bears a superior articular facet, which is for the articulation with the inferior articular facet of first cervical vertebra (atlas). Like the other vertebrae, the axis has a transverse foramen in each transverse process. In the cervical portion of vertebral column, this orifice is for the vertebral artery and vein. On the posterior aspect of its body, it has a short spinous process; the rectus capitis posterior major and the obliquus capitis inferior muscle are attached to the spinous process of the axis.

Below, lateral view of second cervical vertebra, with their different parts

 

Femur

The femur is the longest and thickest bone in the human skeleton. It is tubular, containing abundant marrow. It is covered and moved by the longest, largest and most powerful muscles in the body, such as the sartorius, quadriceps, and adductor magnus muscle. It is commonly known as the thigh bone.

Anatomical Description

The femur is composed of a body (shaft), and two ends: the proximal end and the distal end. The shaft of femur (corpus femoris) is cylindrical, slightly twisted about its axis, and curved forwards. Its anterior side is smooth, while its posterior surface features a rough linea aspera, which is a long ridge of bone that serves as site of attachment to muscles.

The linea aspera is divided into two lips, the lateral and the medial lip. The lateral lip is the continuation of the gluteal tuberosity. However, in the lower third portion of the femur, it runs down laterally as it extends to the lateral condyle. The medial lip, on the other hand, runs down the length of femur but it swerves out medially in the lower third portion of bone as it curves to the medial condyle.

The proximal, or upper, end has two rough protrusions at the junction with the shaft. These protrusions are the greater and the lesser trochanter. The greater trochanter juts out upwards and backwards, making up the lateral part of the proximal end of femur. Meanwhile the lesser trochanter is located on the posteromedial surface of proximal end of the bone. The intertrochanteric line extends between the greater and the lesser trochanter on the anterior aspect of upper end of femur, while the intertrochanteric crest runs on the posterior side between the these two protrusions.

The neck of the femur arises from the medial aspect of its proximal end, between the greater and lesser trochanter. Then it projects upwards and medially, ending up in a spherical portion, which is called the head of femur (caput femoris). The neck is slightly flattened on its frontal plane. The head has a small rough pit, which is called the fossa of the head of femur, where the ligament of the head is attached. The head fits in the acetabulum, which is a cup-shaped cavity on the lateral surface of hipbone (pelvis). They articulate with one another.

The distal or lower end of femur is thick and wide, terminating in two condyles; a medial and a lateral conyle. The medial condyle is larger than the lateral one and they are separated from one another by a deep depression called the intercondylar fossa where the cruciate ligaments are attached. The medial surface of the medial condyle and the lateral surface of the lateral condyle feature a medial epicondyle and a lateral epicondyle respectively, which are small bone projections that serve as attachments for ligaments and tendons.

Below, the anterior side of right femur, with its different parts.

Below, posterior side of right femur. Notice the linea aspera and the lateral and medial lip.

First Cervical Vertebra

The first cervical vertebra is called the atlas. It is the topmost of the seven cervical vertebrae and, therefore, the proximal one of the spinal column. Its vertebral foramen is aligned with the foramen magnum of the base of skull to allow the spinal cord to extend into the cranium as the medulla oblongata.

The first cervical vertebra looks differently from the rest of vertebrae as it lacks the spinous process on its posterior aspect. Rather, it is an irregular ring formed by two arches: the anterior and posterior arch. These are fused to one another by two thick lateral bone masses. On their superior surface, each of these masses bears an oval, concave superior articular facet, which is for the articulation with the occipital bone. Meanwhile, on their inferior surface, they have a flat inferior articular facet, which is for articulating with the superior surface of the second cervical vertebra (axis).

The 1st cervical vertebra anterior arch has an anterior tubercle and small facet for the odontoid process on the posterior surface which articulates with the dens of the axis. The atlas posterior arch has a posterior tubercle, which represents the missing spinous process (spine). Like the rest of the spinal column vertebrae, the atlas has two transverse processes, one on each lateral aspect of it, with an orifice in each one of them; they are for the vertebral arteries, which arise from the subclavian.

Below, the first cervical vertebra (superior aspect).

Below, inferior view of the atlas.