Structure of kidney and ureter Flashcards
Muscular cavity where digestive waste and urine leave the embryo
Cloaca
The kidneys present in embryo development
Pronephros, mesonephros and metanephros
Pronephros
First set of kidneys which regress after 4 weeks and are non functional. They are located in the region of the cervical vertebrae.
What is the composition of the pronephros?
Nephric tubules and nephrotomes
Mesonephros
Temporary and first functional kidneys that form urine. Become part of the urogenital system. They drain into the mesonephric duct/Wolffian duct which eventually regresses. Located in the thoracic/lumbar region.
What does the mesonephros composed of?
Forms urogenital ridge.
Where is the mesonephric system derived from?
Segmented intermediate mesoderm
Metanephros
Located in lower sacral/lumbar region. Contains uretic bud and later, the metanephric blastema.
Where does the bladder develop?
From urogenital region with opening to the allantosis.
Mesonephric duct
Contains the uretic bud to forms the minor calcyx, major calcyx, collecting duct, collecting tubules and ureter
Effect of uretic bud?
Induces differentiation of the mesoderm for formation of the metanephric blastema caps
Renal vesicle
First epithelial derivative of the metanephric blastema. It will from the PCT and DCT first, and develop into the glomerulus, bowman’s capsule and DCT.
Metanephric blastema
Cap forms due to signals from the uretic bud. It gives rise to the nephron from the glomerulus to the DCT via formation of renal vesicle
Renal blood supply during development
Branches from the abdominal aorta and as kidney ascends, it comes directly off abdominal aorta.
Renal artery-> interlobar -> arcuate -> interlobular artery -> afferent arteriole
What are abnormalities that can occur to the kidneys during development?
Kidney develops in pelvis because it does not migrate up
Fusion of the kidneys
Aberrant renal arteries (multiple)
Where does the ureter drain into the bladder?
Superior and posterior
Region where urethra crosses the pelvic floor?
Membranous
What is the majority of the spongy urethra lined with?
Pseudostratified columnar epithelia.
Which part of the urethra is lined with stratified squamous epithelia?
End of urethra in glans penis
Location of kidney anatomically
Retroperitoneal organ from T12 to L3. Right side is lower than the left. Hilum opens anteromedially to abdominal aorta. It is divided into the cortex and the medulla. The functional unit of the kidney is the nephron
What are the anatomical coverings of the kidney?
Enveloped in a tough fibrous connective tissue capsule called the renal capsule which contains perirenal fat. The renal capsule is separated from surrounding pararenal fat by the renal fascia.
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Renal capsule
Renal fascia
Pararenal fat
Which vessel does reabsorption take place in the kidney?
Peritubular capillaries, a branch of the efferent arteriole which surround the PCT and DCT. They drain into the interlobular veins. They are therefore located in the cortical regions of the nephron.
What is pararenal fat?
White adipose tissue located anteriorly to renal fascia
Which vessels are a branch of the afferent arteriole?
Vasa recta capillaries that surround the Loop of Henle for reabsorption in the countercurrent mechanisms. They drain into the renal veins.
Which vessels are a branch of the efferent arterioelle?
Peritubular capillaries, surrounding the PCT and DCT in the cortical region for reabsorption of solutes and secretion into the nephron. They drain into the veins.
Renal fascia
Connective tissue sheath which encloses the kidneys and its structures, extending into the pelvis urethra. It has a midline attachment which prevents inward movement of vessels in renal hilum.
What is perinephric fat?
Brown adipose tissue surrounding kidneys and adrenal glands, separated from pararenal fat via the renal fascia.
What are the important posterior anatomical relations?
Diaphragm is superior to kidney
Medial: psoas major and minor
Posterior: quadratus lumborum
Anterior relations of kidney-right side
Right lobe, hepatic flexure of colon, descending D2 duodenum and hepatorenal pouch
What is the hepatorenal pouch?
AKA pouch of Morrison which is the potential space between the kidney and liver which fills with fluid
How many lobes are in the kidney?
7-9 lobes
What is the blood supply to apical kidney?
Apical segmental -> interlobar -> arcuate -> interlobular
Blood supply to superior lobe of kidney
Anterior Superior segmental -> interlobar -> arcuate -> interlobular
What are the branches of the renal artery?
Renal artery comes off the abdominal aorta and gives off the 5 segmental arteries.
Apical segmental artery
Anterior superior segmental artery
Anterior inferior segmental artery
Posterior segmental artery
Inferior segmental artery.
Blood supply to middle lobe of kidney
Anterior inferior segmental -> interlobar -> arcuate -> interlobular
Blood supply to inferior lobe of kidney
Inferior segmental -> interlobar -> arcuate -> interlobular
Kidney venous drainage
Interlobular vein drains the renal lobe -> arcuate vein -> interlobar vein -> segmental vein -> renal vein
Mesangial cells
Contractile smooth muscles close to the glomerulus which are connected via gap junctions in the kidney. There are two types of mesangial cells:
Intraglomerular
Extraglomerular
What is the intraglomerular mesangial cells?
They are located between the capillaries in the glomerulus and control GFR via vasodilation/constriction.
Which renal vein is longer?
Left renal vein which has two important branches:
Left suprarenal vein.
Left gonadal vein
What is the extraglomerular mesagnial cells?
Forms part of the juxtaglomerular apparatus. It is located between the macula densa and the afferent arteriole. They respond to signals from the macula dens via contraction to release ATP. This will inhibit renin release.
Function of mesangial cells
They are component of the glomerulus which attach to capillaries via cell process to control size of capillary lumen for GFR regulation. They are responsible for pathogen surveillance in the glomerulus and response to glomerular injury by secreting platelet factor
What is the role of the intraglomerular mesangial cells?
They control GFR via vasodilation/constriction that affects the arterioles.
What are the components of the juxtaglomerular apparatus?
Macula densa
Extraglomerular mesangial cells
Juxtaglomerular epitheliod cells
Which structure produces renin?
Juxtaglomerular epitheliod cells which are located in the walls of the afferent arteriole that synthesise renin.
What is the role of the macula densa?
Monitors the Na/CL content of the DCT. In the tuberoglomerular feedback mechanism, high levels of Na/CL means macula densa will inhibit renin production by releases adenosine to act on the extraglomerular mesangial cells to cause vasoconstriction of the afferent arteriole.
Ureter location
Extends from the renal pelvis and is divided into
Abdominal segment
Pelvis segment
Intramural segment
Ureter- descent
Begins from renal pelvis and descends anterior to the psoas major. It crosses pelvic brim when the common iliac artery branches. In the pelvis, it is posterolateral in close proximity to the reproductive organs.
Mesoureter
Sheet of connective tissue surrounding ureter
Structure of ureter
Muscular wall consisting of:
Mucosa: innermost layer formed of transitional epithelia
Inner circular and outer longitudinal Smooth muscle for peristalsis of urine
Adventitia: fibrous connective tissue
What are the natural constrictions of the ureter?
Ureter has 3 natural constrictions:
At the renal pelvis
Crossing of the common iliac into the external iliac artery
Entrance of ureter into bladder wall
What is the innervation to the ureter?
Sympathetic system from T12 -> L1 from the coeliac and renal ganglia.
Parasympathetic supply: pelvic sphlachnic
What is the lymphatic drainage of the kidney?
Aortic and caval lymphatic
What is the pars recta?
Straight descending portion
Composition of Loop of Henle
Simple squamous epithelia
Composition of DCT
Cuboidal epithelia with a few very microvilli with less numerous tubules. Contains granular cells and macula densa cells.
What does the PCT secrete?
Urea, creatinine, drugs and H+ to the lumen to form the filtrate for excretion via the urine.
What does the collecting duct secrete?
H+, drugs and NH4+.
What are the branches of the efferent arterioles?
Peritubular capillaries which reabsorb nutrients from the nephron.
When is prostaglandin stimulated?
Sympathetic system is activated.
How do podocytes prevent protein loss?
Podocyte have long foot processes in contact with the glomerular basement membrane, and contain the negatively charged glycocalcyx protein rich in sialic acid to form a layer that repels proteins.
What is the histology of the prostatic urethra?
Transitional epithelia.
What is the histology of the membranous urethra?
Pseudostratified columnar epithelia
What is the histology of the spongy urethra?
Stratified squamous epithelia.
What is the histological structure of the kidneys?
Formed of the glomerulus, a network of capillaries lined with a thin endothelium that is fenestrated with a central mesangium and a basement membrane .The basement membrane is important for the repulsion of macromolecules and is formed of type IV and V collagen and glycosaminoglycans which regulate the movement of charged molecules.
What is the role of the mesangium?
Responds to signals from angiotensin II and thromboxane in order to contract and prevent filtration of substances in the glomerulus and reduce GFR.
Prostaglandin inhibits the contraction of the mesangium and promotes a higher GFR.
What are the components of the glomerulus?
Podocyte, mesangium, endothelium and glomerular basement membrae
What is the primary innervation to the kidneys?
Coeliacs plexus and greater splanchnic nerves, from the thoracolumbar splanchnic nerves.
