SYSTEMA URINARIA – URINARY SYSTEM – URINARY SYSTEM
The main task of the urinary system is to provide the balance of the internal environment of the body by providing selective control of the excretion or accumulation of minerals (Na, K, etc.) and water dissolved in the blood. (Homeostasis) is to protect. In addition to the water and mineral balance, metabolic wastes, some of which are toxic (eg Urea, etc.), are passed out of the body through the kidneys through the urine. Kidneys perform their Homeostatic duty with Filtration (filtration), Resorption (reabsorption) and Excretion (secreting, excreting) functions. The urinary system consists of a pair of kidneys that produce urine and the conductive pathways consisting of the ureters, bladder and urethra. We will examine these separately.
1. KIDNEYS – RENES
Kidneys are called ORGANA UROPOETICA, meaning the organ that produces urine, since they produce 2 – 2.5 liters of urine from the 1700 liters of blood that comes to them per day with the functions of Filtration, Resorption and Excretion. Kidneys, a right-left double organ, are located behind the Peritoneum (in the retroperitoneal position), leaning against the posterior abdominal wall on both sides of the spine. Topographically, the Right kidney is located at the T-12 – L-3 level, and the Left kidney at the T-11 – L-2 level.
Kidneys are bean-like. Each kidney has a convex outer edge and a concave inner edge on both anterior and posterior surfaces. On the inner edge (Margo medialis) there is a vertical slit (hilus renale) for formations that enter and exit the kidney. A space called the Sinus renalis extends from the hilus renale into the kidney. The structures in the hilus renale are ordered from anterior to posterior as V. renalis, A. renalis, and ureter.
The average weight of a kidney in an adult is 130-150 g. Its dimensions are 12 x 6 x 3 cm.
Each kidney is surrounded by a three-layered support and covering tissue.
1.The inner covering called Capsula fibrosa (Renal capsule) surrounds the kidney from the outside, is a solid, fibrous tissue layer with low expansion ability.
2. Capsula adiposa (Perirenal fat capsule) is the middle layer and surrounds Capsula fibrosa from the outside. Capsula adiposa protects the kidney against impacts.
3. Tunica fibrosa (Fascia renalis), the outermost covering, is considered to be formed by the condensation of the Extraperitoneal adipose tissue in the abdominal wall, Fascia subserosa. The perirenal fascia helps the kidney to stay in its normal position. It has two leaves, Fascia prerenalis and Fascia retrorenalis.
Behind the kidney, outside the perirenal fascia, is the Pararenal fat capsule (Corpus adiposum pararenale). Fascia renalis is surrounded anteriorly by the Parietal peritoneum.
STRUCTURE OF THE KIDNEYS
When a frontal incision is made to the kidney, three different regions are distinguished from the inside out.
1.Pelvis renalis
2.Medulla renalis
3.Cortex renalis
Pelvis renalis, the top of which extends from the Hilus renale with the ureter, its body is seated in the Sinus renalis and a funnel-shaped section made of membranes.
Pelvis renalis, proximally extends into the kidney tissue in the form of large and small calyces (Calix renalis majoris et minoris).
Small and large calyces form the excretory tree called Pelvis renalis and Ureter arbor excretorius.
Medulla renalis, which covers approximately 2/3 of the kidney mass, contains 8-18 (average 12) pyramidal structures. Pyramidal formations with bases of Cortex renalis and tops of small calyces are called Pyramis renalis (Pyramids of Malpighi).
Malpighi pyramids contain the distal tubules and collecting tubules of the Nephron. In the dissection of fresh anatomy cadavers, these formations are called Processus ferreini.
These Pyramidal tubes concentrate the urine by reabsorption of the water in the filter material inside them. The collecting pipes open to the larger Ductus papillaris (Bellini canal) and the Ductus papillaris to the small calyces via the Foramen papillaris at the top of the Pyramids.
The outer layer (Cortex renalis), which covers 1/3 of the kidney mass, consists of numerous straight and curved tubules, blood vessels and visible spherical structures (Corpusculum renale).
The outer part of the cortex close to the kidney capsule is called Zona externa (Regio corticalis), and the inner part close to the Malpighi pyramids is called the Zona interna (Regio juxtamedullaris).
There is also a darker cortical tissue between the Malpighian pyramids. These columns separating the pyramids from each other are called Columnae renales. A Pyramis renalis and its surrounding cortical structure are collectively called Lobus renalis.
BLOODING OF THE KIDNEYS
The kidneys receive much more blood than any other organ of the same size in our body. This is because the kidneys are the main organs that clean the blood from harmful waste materials.
The kidneys, using 20-25% of the heartbeat, take 1.2 liters of blood per minute, about 1700 liters per day. Our blood passes through the kidneys 340 times a day and is purified from harmful waste materials. During this process, one tenth of 1700 liters of blood (approximately 170 liters) of Glomerular filtrate and 1% of Glomerular filtrate of 1.7 liters of urine are formed.
The kidney’s arterial blood supply is provided by A. renalis, the largest double branch of the Aorta abdominalis. Each Renal artery arises from the Aorta abdominalis at the level of L-1 – L-2 vertebrae just below the superior A. mesenterica. The right renal artery is longer. Reaching the hilus renale, the renal artery divides into anterior and posterior sections, and a total of 5 segmental branches in these sections. Since there are no anastomoses between the segmental branches to provide nutrition, segmental necrosis occurs when they are attached.
Abarrant (non-normal) segmental arteries come to kidney segments at a rate of 30-35%.
Venous blood of kidney drains to V. cava inferior via Cavum renalis.
The innervation of the kidneys is provided by the Plexus renalis. In men, there are connections between the fibers of this Plexus and the nerves coming from the Testis.
Similar to lung and liver, kidney has segmental structure. Kidney segments are 5 in number. These are
1.Segmentum superius
2.Segmentum inferius
3.Segmentum anterius superius
4.Segmentum anterius inferius
5.Segmentum posterius.
2. URETER
Ureters are two thin muscular tubes 25-30 cm long that carry urine from Ppelvis renalis to Vesica urinaria (urinary bladder).
Ureters extending vertically along the transverse processes of L-2 – L-5 vertebrae, leaning on M. psoas majors, cross the iliac vessels (Vasa iliacae) and enter the pelvic cavity. Here, the ureters, which first continue their way on the Pelvis wall, then turn towards the midline and enter the urinary bladder. The hole in the bladder of each is called the ostium ureteris. Before the ureters enter the bladder, Duc. deferens, and in females, A. uterina. These crosses (especially the cross of A. uterina) have surgical importance. Along their course, three divisions of the Ureters are distinguished: Abdominal, Pelvis and Intra-Wall.
1.Abdominal part (Pars abdominalis): It is the part from the uretero-pelvic junction (the beginning of the ureter) to the place where it crosses the iliac vessels (or Linea terminalis).
2.Pelvic section (Pars pelvica): It is the section from where the ureter crosses the iliac veins to the point where it enters the urinary bladder.
3. Intra-wall section (Pars intramuralis): It is the shortest part of the ureter, 1.5-2 cm, located in the wall of the urinary bladder.
Ureters have 3 natural strictures. The upper stenosis is at the uretero-pelvic junction, the middle stenosis is where it crosses the iliac vessels, and the lower stenosis is at the Pars intramuralis. The lower stenosis is considered the narrowest part of the ureter, where the Stones are most often worn.
STRUCTURE OF THE URETER
The wall structure of the ureter is in principle the wall structure of the hollow organs.
Tunica mucosa, the inner layer, is made of stratified variable epithelium – Urethelium and does not contain glands.
Middle layer – Tunica muscularis is a two-layer smooth muscle layer, inner Longitudinal and outer Circular.
In the lower 1/3, there is an additional outer Longitudinal layer.
Periodic peristaltic contractions in the tunica muscularis assist in the delivery of urine to the bladder.
The outer layer, Tunica adventitia, is made of loose connective tissue.
3. URINARY SAC – VESICA URINARIA – BLADDER
Urine bladder (Vesica urinaria – Cystis), where the urine coming through the ureters is kept for a certain period of time, transmitted to the Urethra when necessary, 300-500 ml It is a voluminous, hollow muscular organ.
Vesica urinaria is located at the floor of the Pelvic cavity posterior to the Symphysis pubis in the Retroperitoneal location like the kidneys and ureters.
It is located on the Prostate in front of the Rectum in men, and in front of the Uterus and Vagina in women. Between the Symphysis pubis and the Bladder is the Spatium prevesicale (Retzius space).
The urinary bladder has 4 sections.
1.Apex vesicae: It is the pointed upper part of the urinary bladder and is adjacent to the Symphysis pubis or anterior abdominal wall according to its fullness. Liga tortoiseshell, extending from the apex to the navel. The umbilicale is called the medianum. This ligament is the remnant of Urachus.
2.Fundus vesicae: It is the posterior lower part of the urinary bladder and the right-left ureter opens here. On the inside is Trigonum vesicae. The ureters (Ostium ureteris) open to the upper corners of this triangle, and the Ostium urethrae internum starts from the lower corner.
3.Corpus vesicae: It is the largest part of the urinary bladder between the Apex and Fundus.
4.Cervix vesicae: The lowest narrow part of the urinary bladder is Cervix (bladder neck) and extends with the Uretra. The starting hole of the urethra is called Ostium urethrae internum.
WALL STRUCTURE OF THE URINARY SAC
The wall structure of the urinary bladder is also three-layered, like the wall structure of the urinary tract. There is Tunica mucosa inside, Tunica muscularis in the middle, Tunica serosa (Tunica adventitia) outside.
Tunica mucosa: It is a thick alternating epithelial layer and contains folds in all parts except Trigonum vesicae.
Tunica muscularis: It is a three-layer smooth muscle layer. It is collectively called M. detrussor vesicae. Tunica muscularis is made of inner and outer Longitudinal muscle fibers with circular course in the middle. When M. detrusor vesicae contracts, the volume of the urinary bladder decreases and the urine in it is sent to the urethra. Circular fibers form the internal urethra sphincter (M. sphincter vesicae or M. sphincter urethrae internum) at the neck of the bladder. Parasympathetic stimulation relaxes this sphincter while contracting M. detrusor vesicae, it is called Mictio, Urinatio, Urination.
Tunica serosa: Only the upper and lateral surfaces are surrounded by a serous layer derived from the Peritoneum, while the other parts are surrounded by Tunica adventitia, which consists of loose connective tissue.
4. URETRA
Uretra (Urethra) is a mucous-lined, muscular tube that serves to expel the urine collected in the urinary bladder. This route, through which only the urine passes in women, is also used in men for excretion of Ejaculate when necessary.
Urethra has two holes. The hole that opens into the urinary bladder is called Ostium urethrae internum, and the hole that opens out is called Ostium urethrae externum.
There are differences in shape, size and functionality between male and female Urethra.
1.Urethra feminina – Female urethra: It is a 3-4 cm long tube, starting from the neck of the urinary bladder, passing through the posterior-lower part of the Syphysis pubis and ending in the Vulva. The female urethra has Pelvic, Membranous, and Perineal sections.
2.Urethra masculina – Male urethra: It is a 20 cm long tube extending between the Ostium urethrae internum at the neck of the urinary bladder and the Ostium urethrae externum at the top of the Glans penis. The male urethra is the element of both the Urinary and Genital systems. It has three sections along the male urethra tract: Prostatic, Membranous, and Spongiose.
Pars prostatica: It is the first 3-4 cm part of the urethra that passes through the prostate gland. duc. Ejeculatorius and Prostate’s drainage channels open here. The widest part of the uretra is Pars prostatica. On the posterior wall of this section, there is a longitudinal mucosal fold (Crista urethralis) and a ridge (Colliculus seminalis) in the middle.
Pars membranacea: It is the shortest and narrowest part of the urethra that crosses the Diaphragma urogenitale. Here is the Sphincter urethrae (voluntary work).
Pars spongiosa (Anterior urethra): It is the longest part of the urethra, 15-16 cm, located in the Corpus spongiosum penis. It is also called penile urethra.
Gl. The discharge duct of the bulbourethralis opens into the initial part of the penile urethra. The enlargement in the first part of the pars spongiosa is called Fossa bulbaris, the enlargement in the glans penis is called Fossa navicularis.
URETRA CLINICAL INFORMATION
1. In case of rupture of the urethra in the superficial Perineum space (extravasation), the flow directions of the urine also show the attachment sites of the Perineum fascia. Urine goes up to the anterior abdominal wall. It also spreads within the areolar tissue around the Scrotum and Penis. Does not extend into the Thigh or Anal triangle. Because the Scrapa fascia attaches to the Inguinal ligament before continuing with the Fascia latae. Since the fascia M. transversus perinei superficialis is folded from its anterior surface to its posterior surface and wraps it like a bag, urine does not pass into the anal region.
2.Fossa ischiorectialis is the site of infections that can cause ischiorectal abscesses. These abscesses are uncomfortable and painful.
The parts of the adipose tissue filling the ischiorectal fossa close to the rectum are open to infection. Infection can spread from
1. Anal sinus infection (Cryptoid),
2. Pelvi-rectal abscesses,
3. Anal mucosal ruptures. There is pain along with a feeling of fullness and tension between the anus and the Tuber ischiadicum. These abscesses can spontaneously make Fistula
1. Anal canal,
2. Rectum,
3. Perineum skin near the anus and to some or all of these parts. Ischio-rectal abscess of one side may pass behind the Anus into the opposite fossa.
Wishing you a healthy day…
Specialist Dr.Ali AYYILDIZ – Veterinarian – Human Anatomy Specialist Dr. (Ph.D.)
