pediagenosis: science
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Showing posts with label science. Show all posts
Showing posts with label science. Show all posts

Wednesday, November 13, 2019

Arteries and Veins of Perineum: Male Anatomy

Arteries and Veins of Perineum: Male Anatomy


Arteries and Veins of Perineum: Male Anatomy
Dartos fascia of scrotum, Septum of scrotum, Posterior scrotal arteries, Deep (Buck’s) fascia of penis, Superficial perineal (Colles’) fascia (cut edge), Superficial perineal space (opened), Perineal artery and vein, Internal pudendal artery passes superior to perineal membrane, Superficial transverse perineal muscle and transverse perineal artery (cut and reflected), Internal pudendal vessels and pudendal nerve (cut) in pudendal canal (Alcock’s) (opened up), 

Monday, November 11, 2019

MEDIASTINUM

MEDIASTINUM


MEDIASTINUM
The mediastinum is that portion of the thorax that lies between the right and left pleural sacs and is bounded ventrally by the sternum and dorsally by the bodies of the thoracic vertebrae. The superior boundary of the mediastinum is defined by the thoracic inlet, and its inferior boundary is formed by the diaphragm. By convention, the mediastinum is divided into superior and inferior parts by a plane extending horizontally from the base of the fourth vertebral body to the angle of the sternum. The superior mediastinum contains the aortic arch; the brachiocephalic (innominate) artery; the beginnings of the left common carotid and left subclavian arteries; the right pulmonary artery trunk; the right and left brachiocephalic (innominate) veins as they come together to form the superior vena cava; the trachea with right and left vagus, cardiac, phrenic, and left recurrent laryngeal nerves; the esophagus and the thoracic duct; most of the thymus; the superficial part of the cardiac plexus; and a few lymph nodes.
BRONCHIAL ARTERIES

BRONCHIAL ARTERIES


BRONCHIAL ARTERIES
The lungs receive blood from two sets of arteries. The pulmonary arteries follow the bronchi and ramify into capillary networks that surround the alveoli, allowing exchange of oxygen and carbon dioxide. The bronchial arteries derive from the aorta. They supply oxygenated blood to the tissues of the lung that are not in close proximity to inspired air, such as the muscular walls of the larger pulmonary vessels and airways (to the level of the respiratory bronchioles) and the visceral pleurae. The origin of the right bronchial artery is quite variable. It arises frequently from the third right posterior intercostal artery (the first right aortic intercostal artery) and descends to reach the posterior aspects of the right main bronchus. It may arise from a common stem with the left inferior bronchial artery, which origi- nates from the descending aorta slightly inferior to the point where the left main bronchus crosses it. Or it may arise from the inferior aspect of the arch of the aorta and course behind the trachea to reach the posterior wall of the right main bronchus.
RELATIONSHIPS OF THE TRACHEA AND MAIN BRONCHI

RELATIONSHIPS OF THE TRACHEA AND MAIN BRONCHI


RELATIONSHIPS OF THE TRACHEA AND MAIN BRONCHI
The trachea begins at the lower border of the larynx (just below the cricoid cartilage) at about the level of the sixth cervical vertebra and ends at about the level of the upper border of the fifth thoracic vertebra, where it divides into the two main bronchi. The thyroid gland lies on the anterior and both lateral aspects of the highest part of the trachea.
Medial Surface Of The Lungs

Medial Surface Of The Lungs


Medial Surface Of The Lungs
The medial (mediastinal) surfaces of the right and left lungs present concave mirror images of the right and left sides of the mediastinum so that in addition to the structures forming the root of the lung, the medial lung surface presents distinct impressions made by the structures constituting the mediastinum (see Plates 1-18 and 1-19).
Bronchopulmonary Segments

Bronchopulmonary Segments


Bronchopulmonary Segments
A bronchopulmonary segment is that portion of the lung supplied by the primary branch of a lobar bronchus. Each segment is surrounded by connective tissue that is continuous with visceral pleura and forms a separate, functionally independent respiratory unit. The artery supplying a segment follows the segmental bronchus but the segmental veins are at the periphery of the segment and thus can be helpful in delineating it.
Circulatory System: Heart Chambers

Circulatory System: Heart Chambers


Circulatory System: Heart Chambers
Time period: day 22
Dividing the heart into chambers
Heart septa appear during week 5 and divide the heart tube into four chambers between days 27 and 37. The septa form as inward growths of endocardium separating the atrial and ventricular chambers, splitting the atrium into left and right, and splitting the ventricle and bulbus cordis into left and right ventricles, respectively (Figure 28.1). The atrioventricular canal connects the primitive atrium and ventricle. At the end of week 4 the endocardium of the anterior and posterior walls of the atrioventricular canal thicken and bulge outwards into the canal’s lumen. These are the endocardial cushions and by the end of week 6 they meet in the middle, splitting the atrioventricular canal into two canals (Figure 28.1).
Formation Of The Heart Tube

Formation Of The Heart Tube


Circulatory System: Heart Tube
Time period: days 16–28
Formation Of The Heart Tube
During the third week of development blood islands appear in the lateral plate mesoderm (Figure 27.1) from angioblasts that accumulate as a syncytium (rather like the formation of the syncytiotrophoblast that we saw form during the development of the placenta in Chapter 13). From these cells new blood cells and blood vessels form through vasculogenesis. Blood islands at the cranial end of the embryo merge and assemble a horseshoe‐shaped tube lined with endothelial cells which curves around the embryo in the plane of the mesoderm.

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