|
|
Distribution.
Lymphatic capillaries are abundant in the dermis where they form superficial and deep plexuses, the former sending blind ends into the dermal papilli. The plexuses are especially rich over the palmar surface of the hands and fingers and over the plantar surface of the feet and toes. The epidermis is without capillaries. The conjunctiva has an especially rich plexus.
The subcutaneous tissue is without capillaries.
The tendons of striated muscle and muscle sheaths are richly supplied. In muscle, however, their existence is still disputed.
The periosteum of bone is richly supplied and they have been described in the Haversian canals. They are absent in cartilage and probably in bone marrow.
The joint capsules are richly supplied with lymphatic capillaries, they do not, however, open into the joint cavities.
Beneath the mesothelium lining of the pleural, peritoneal and pericardial cavities are rich plexuses; they do not open into these cavities.
The alimentary canal is supplied with rich plexuses beneath the epithelium, often as a superficial plexus in the mucosa and a deeper submucosal plexus. Cul-de-sacs extend into the filiform papilli of the tongue and the villi of the small intestine. Those portions of the alimentary canal covered by peritoneum, have in addition a subserous lymphatic capillary plexus beneath the mesothelium.
Lymph capillaries of the human conjunctiva: a, conjunctiva cornei; b, conjunctiva sclerotici. X 40 dia. (Teichmann.)
(See enlarged image)
Lymph capillaries from the human scrotum, showing also transition from capillaries to the collecting vessels a, a. X 20 dia. (Teichmann.)
(See enlarged image)
The salivary glands are supplied with lymphatic capillaries.
The liver has a rich subserous plexus in the capsule and also extensive plexuses which accompany the hepatic artery and portal vein. The lymphatic capillaries have not been followed into the liver lobules. The lymph from the liver forms a large part of that which flows through the thoracic duct. The gall-bladder and bile ducts have rich subepithelial plexuses and the former a subserous plexus.
The spleen has a rich subserous set and a capsular set of lymphatic capillaries. Their presence in the parenchyma is uncertain.
Lymph capillaries of the cutis from the inner border of the sole of the human foot. a, a, outer layer; b, b, inner layer. X 30 dia. (Teichmann.)
(See enlarged image)
The nasal cavity has extensive capillary plexuses in the mucosa and submucosa.
The trachea and bronchi have plexuses in the mucosa and submucosa but the smaller bronchi have only a single layer. The capillaries do not extend to the air-cells. The plexuses around the smaller bronchi connect with the rich subserous plexus of the lungs in places where the veins reach the surface.
Vertical section through human tongue; a, a, blind lymph capillaries in the filiform papilli with the underlying lymphatic plexus. X 45.
(See enlarged image)
Lymphatics have been described in the thyroid gland and in the thymus.
The adrenal has a superficial plexus divided into two layers, one in the loose tissue about the gland and the other beneath the capsule. Capillaries have also been described within the parenchyma.
The kidney is supplied with a coarse subserous plexus and a deeper plexus of finer capillaries in the capsule. Lymphatics have been described within the substance of the kidney surrounding the tubules.
The urinary bladder has a rich plexus of lymphatic capillaries just beneath the epithelial lining, also a subserous set which anastomoses with the former through the muscle layer. The submucous plexus is continuous with the submucous plexus of the urethra.
The prostate has a rich lymphatic plexus surrounding the gland and a wide-meshed subcapsular plexus.
The testis has a rich superficial plexus beneath the tunica albuginea. The presence of deep lymphatics is disputed.
The uterus is provided with a subserous plexus, the deeper lymphatics are uncertain. Subepithelial plexuses are found in the vagina.
The ovary has a rich superficial plexus and a deep interstitial plexus.
The heart has a rich subserous plexus beneath the epicardium. Lymphatic capillaries have also been described beneath the endocardium and throughout the muscle.
Lymphatic capillaries are probably absent in the central nervous system, the meninges, the eyeball (except the conjunctiva), the orbit, the internal ear, within striated muscle, the liver lobule, the spleen pulp and kidney parenchyma. They are entirely absent in cartilage. In many places further investigation is needed.
|
|
