Logan Steele
The ureter is a fibromuscular tube that transports urine from the kidneys to the bladder. It is surrounded by two muscular layers, an inner longitudinal layer of muscle and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer. The ureter is lined by urothelium, a type of transitional epithelium that can respond to stretches in the ureter. The ureter is supplied by the spinal cord, with parasympathetic inputs from the superior hypogastric plexus, pelvic splanchnic nerves, and the inferior hypogastric plexus.
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What You'll Learn
The ureter is a fibromuscular tube
The ureter has a complex structure, with three main tissue layers: the inner mucosa, the middle muscle layer, and the outer serosa. The inner mucosa is lined with urothelial cells, a form of transitional epithelium that can respond to stretches in the ureter. The middle muscle layer, or muscularis, is composed of smooth muscle fibres in different orientations, including inner longitudinal, middle circular, and outer longitudinal layers. The outer serosa, or adventitia, is composed of fibroelastic tissue and houses the ureter's blood supply, lymphatics, and nerves.
The ureter receives its blood supply from various arteries, including the renal, gonadal, common iliac, and internal iliac arteries, as well as branches from the abdominal aorta. The ureter's nerve supply, or innervation, involves the lower thoracic, lumbar, and sacral segments of the spinal cord, with contributions from the superior and inferior hypogastric plexuses. The ureter also contains pacemaker cells that initiate ureteral peristalsis, which is the wave-like motion that propels urine towards the bladder.
The ureter plays a crucial role in the urinary system, ensuring the smooth passage of urine from the kidneys to the bladder. Its fibromuscular composition, with multiple layers of muscle, enables peristalsis and prevents reflux, ensuring the efficient and one-way flow of urine. The ureter's structure and function are highly specialised, and it is susceptible to various conditions such as urinary tract infections, kidney stones, and congenital abnormalities.
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The ureter has a muscularis layer
The ureter is a tubular structure that passes urine from the kidneys to the bladder. It is composed of several layers, including the mucosa (innermost layer), muscularis (middle layer), and adventitia (outer layer).
The ureter's muscularis layer is made up of smooth muscle fibres oriented in different directions, forming an inner longitudinal layer, a middle circular layer, and an outer longitudinal layer. This muscular coat surrounds the mucosa, which is lined by urothelium, a type of transitional epithelium. The ureter's muscular layers are responsible for the peristaltic activity that moves urine from the kidneys to the bladder.
The ureter's wall is made up of three main tissue layers: the inner mucosa, the middle muscularis layer, and the outer serosa. The inner mucosa is lined by a transitional epithelium, which allows it to respond to stretches in the ureter. The middle muscularis layer is composed of smooth muscle fibres, which provide the necessary contraction for the ureter's peristaltic activity. The outer serosa layer is composed of fibroelastic tissue and houses the ureter's blood supply, lymphatics, and nerves.
The ureter's smooth muscle fibres are supplied by the lower thoracic, first lumbar, and second to fourth sacral segments of the spinal cord. These muscles receive motor impulses from intrinsic smooth muscular pacemaker sites, which govern the ureter's peristalsis. The ureter's peristaltic waves originate in the proximal upper urinary tract and propagate towards the urinary bladder.
The ureter's muscularis layer is essential for the proper functioning of the ureter, providing the necessary contraction and peristalsis to transport urine from the kidneys to the bladder. This layer is surrounded by other critical structures, including blood vessels, lymphatics, and nerves, which all contribute to the ureter's overall function and health.
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The ureter's blood supply
The ureters are two thick tubes that carry urine from the kidneys to the bladder. They are about 25 cm long and are located bilaterally, with one ureter draining each kidney. The ureters are a critical landmark and are closely associated with other vessels and organs, which makes accidental injury to the ureters a serious risk during surgery.
The ureters receive blood from multiple arterial branches. The abdominal aorta and renal, gonadal, and common iliac arteries supply the abdominal ureter. The distal ureteral parts receive circulation from the vesical and uterine arteries, which are internal iliac artery branches. The arteries course along the ureter, creating an anastomotic plexus. This arterial network allows for the safe mobilisation of the ureter during surgery. The ureter's venous and lymphatic drainage mirrors that of the arterial supply. The lymphatic vessels empty into the internal, external, and common iliac nodes. The left ureter's lymphatic drainage courses to the left paraaortic lymph nodes.
The ureters have an expansive anastomosing network of arterial supply and venous drainage along their length. The proximal end receives arterial supply from the ureteric branch of the renal artery. Contributions from the ovarian artery (testicular artery in males) as well as a direct ureteric branch from the abdominal aorta supply the middle segment. The distal portion receives its arterial supply from ureteric branches from both the superior and inferior vesical arteries. They are drained by accompanying veins.
The ureter is surrounded by two muscular layers, an inner longitudinal layer of muscle, and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer. Beyond these layers sits an adventitia containing blood vessels, lymphatic vessels, and veins. The ureteric nerves form a plexus in the adventitia of the ureter that receives branches from the renal and aortic plexuses (in its upper part); the superior hypogastric plexus and hypogastric nerve (in its intermediate part); and the hypogastric nerve and inferior hypogastric plexus (in its lower part).
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The ureter's nerve supply
The ureters are two thick tubes composed of smooth muscle that transport urine from the kidneys to the urinary bladder. They are lined with urothelial cells, a form of transitional epithelium, and feature an extra layer of smooth muscle in the lower third to aid in peristalsis. The ureters are surrounded by two muscular layers, an inner longitudinal layer of muscle, and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer. The ureter is supplied by the lower three thoracic, first lumbar, and the second to fourth sacral segments of the spinal cord by branches from the renal and abdominal aortic plexuses, and the superior and inferior hypogastric plexuses. The ureteric nerves form a plexus in the adventitia of the ureter that receives branches from the renal and aortic plexuses (in its upper part); the superior hypogastric plexus and hypogastric nerve (in its intermediate part); and the hypogastric nerve and inferior hypogastric plexus (in its lower part).
The ureter receives both sympathetic and parasympathetic innervation. The sympathetic inputs come from the thoracolumbar preganglionic segments, which synapse with the aorticorenal and inferior and superior hypogastric sympathetic plexuses before innervating the ureter. Parasympathetic inputs derive from the S2-S4 segments. Experimental data indicate that autonomic nerves have a minimal role in the propagation of peristalsis. Instead, they likely modulate the contractile events occurring within the upper urinary tract musculature. The predominant mechanism responsible for impulse propagation is myogenic conduction, mediated by electrotonic coupling between adjacent smooth muscle cells via intercellular gap junctions.
The blood supply to the ureter is segmental. The ureteral portion closest to the kidneys receives blood directly from the renal arteries. The middle part of the ureter is supplied by the common iliac arteries, direct branches from the abdominal aorta, and gonadal arteries; the gonadal arteries being the testicular artery in men and the ovarian artery in women. The lower third of the ureter, closest to the bladder, is supplied by branches from the internal iliac arteries, mainly the superior and inferior vesical arteries. The arterial supply can be variable, with arteries that contribute including the middle rectal artery, branches directly from the aorta, and, in women, the uterine and vaginal arteries. The arteries that supply the ureters end in a network of vessels within the adventitia of the ureters.
The ureters leave the kidneys posterior to the renal vessels. Both ureters pass inferiorly over the abdominal surface of the psoas major, with the genitofemoral nerve behind it and the vessels of the gonads in front. As the right ureter travels towards the bladder, it travels posterior to the duodenum and further down it is crossed by branches of the superior mesenteric vessels. The left ureter, however, travels laterally to the inferior mesenteric vessels and is subsequently crossed by its branches. Eventually, the vessels leave the psoas major as the common iliac arteries bifurcate to enter the true pelvis. The ureter pierces through the wall of the urinary bladder from lateral to medial and posterior to anterior.
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The ureter's lymphatic drainage
The ureters are muscular tubes that transport urine from the kidneys to the urinary bladder. They are lined with urothelial cells, a form of transitional epithelium, and feature an extra layer of smooth muscle in the lower third to aid in peristalsis. The ureters are surrounded by two muscular layers, an inner longitudinal layer of muscle, and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer.
The lymphatic drainage of the proximal part of the ureters is similar to that of the kidneys, and therefore drains into the lateral caval nodes on the right, or lateral aortic nodes on the left. Distally, they drain to the internal and external iliac nodes. The middle segment drains to the common iliac and precaval/preaortic nodes. All lymph drained from the ureters eventually makes its way to the cisterna chyli and thoracic duct before returning to systemic circulation. Obstruction of the upper ureter can result in pooling of water in the renal pelvis, a condition called hydronephrosis. This, in turn, causes the ureters to become distended and the patient will experience pain along the tip of the 9th costal cartilage to the end of the common iliac artery.
The ureteric nerves form a plexus in the adventitia of the ureter that receives branches from the renal and aortic plexuses (in its upper part); the superior hypogastric plexus and hypogastric nerve (in its intermediate part); and the hypogastric nerve and inferior hypogastric plexus (in its lower part). The ureter receives parasympathetic supply from the superior hypogastric plexus, pelvic splanchnic nerves, and the inferior hypogastric plexus.
The ureter is supplied from the lower three thoracic, first lumbar, and the second to fourth sacral segments of the spinal cord by branches from the renal and abdominal aortic plexuses, and the superior and inferior hypogastric plexuses. The ureter's blood supply is segmental. The ureteral portion closest to the kidneys receives blood directly from the renal arteries. Abdominal aortic branches and the common iliac and gonadal arteries supply the middle part. The ureters' most distal segment receives circulation from internal iliac artery branches.
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Frequently asked questions
The ureter is a fibromuscular tube that conveys urine from the kidneys to the bladder.
The ureter is a tube composed of smooth muscle. It has two muscular layers—an inner longitudinal layer of muscle, and an outer circular or spiral layer of muscle. The lower third of the ureter has a third muscular layer.
The ureter transports urine from the kidneys to the urinary bladder.
