What are the 2 borders, 2 surfaces, and 2 poles of the kidney?
Borders:
- lateral (convex)
- medial (concave, with renal hilum)
Surfaces:
- anterior
- posterior
Poles:
- upper
- lower
Which structures enter the kidney at the renal hilum, and in which order?
From anterior to posterior:
- renal vein
- renal artery (with ANS nerves and lymphatics)
- renal pelvis
Where is the kidney located?
At T12-L3 level on the posterior abdominal wall, with the upper lobes within the floating ribs
- left: rib 11 on upper pole
- right: rib 12 on upper pole
(right lower than left because of liver)
What are the tissue layers of the kidney?
Retroperitoneal:
- anterior surface covered by parietal peritoneum
Deep to superficial:
- fibrous capsule
- perinephric fat (cushions kidney)
- renal fascia (anchors kidney and adrenal gland to surrounding structures
Which organs lie in relationship to the kidneys?
Posterior surfaces (both kidneys):
- medial: psoas
- intermediate: QL
- lateral: TA
Anterior surface (right):
- hepatic area (superior)
- right colic flexure (middle)
- duodenum (medial)
- small intestine (inferior)
Anteerior surface (left):
- gastric surface (superior)
- pancreatic (middle)
- small intestine (inferior)
- spleen (supero-lateral)
- descending colon (infero-lateral)
What are the lobes of the kidney?
There are 8 lobes per kidney
Lobe = medullary pyramid + surrounding cortical tissue
Describe the 4 major components of the internal anatomy of the kidney
Cortex:
- external layer of tissue beneath capsule
- inward extensions of cortical tissue form renal columns
Medulla:
- internal component of kidney
- pyramids: have a papilla (apex) and a base, and a striated appearance due to parallel bundles of urine collecting ducts
- renal columns projecting between pyramids from cortex
Chalyces:
- urine drains from papillae of renal pyramids into several minor chalyces
- minor chalyces converge into 2-3 major chalyces, which empty into renal pelvis
Renal pelvis:
- receives urine from the major chalyces
- continuous with ureter leaving hilum
Which are the arteries that supply and flow through the kidney, in order from largest to smallest?
Renal arteries Segmental arteries Interlobar arteries Arcuate arteries Afferent arteriole (through glomerulus) Efferent arteriole
Describe the steps of blood circulation through the kidney
Renal arteries Segmental arteries Interlobar arteries Arcuate arteries Interlobular Afferent arteriole (through glomerulus) Efferent arteriole Peritubular capillaries or vasa recta
Interlobular veins Arcuate veins Interlobular veins Renal vein Inferior vena cava
Briefly describe the renal arteries and renal veins
Renal arteries:
- arise from aorta at L1-2
- (right longer than left)
- enter renal sinus and divide into smaller branches
Renal veins:
- formed by 5-6 interlobular veins
- left longer than right (crosses aorta); and joined by Lt suprarenal v and Lt gonadal v before draining into IVC
What is the nerve supply of the kidney?
PNS: CNX Vagus
SNS: T10-12 splanchnic nerves
Visceral afferents
What is the lymphatic drainage of the kidney?
Para-aortic nodes (near origins of renal arteries)
What is a nephron?
The basic functional unit of the kidney (1 million per kidney)
- made up of a renal corpuscle (glomerulus and glomerular capsule), a renal tubule (proximal convoluted, nephron loop and distal convoluted tubule), and a collecting duct
What are the functions of a nephron?
Blood filtration and urine formation
What are the components of a renal corpuscle?
Glomerulus and glomerular capsule
Glomerulus:
- a knot of capillaries
- fenestrations (capillary pores) allow for the easy formation of filtrate
- blood supplied by an afferent arteriole and drained by an efferent arteriole
Glomerular capsule:
- encloses glomerulus
- continuous with renal tubule
- podocytes: specialized epithelial cells with foot processes that cling to capillaries
What are the components of a renal tubule?
Proximal convoluted tubule
Nephron loop
Distal convoluted tubule
Describe the 2 types of nephrons
Cortical
- majority (85%)
- primarily in cortex with only a short extension into medulla
- feed into peritubular capillaries
Juxtamedullary
- minority (15%)
- originate close to cortex-medulla junction and extend deep into medulla
- feed into vasa recta
Describe the antaomy of a renal tubule
Proximal convoluted tubule:
- receives filtrate from glomerular capsule
- cuboidal cells have microvilli and mitochondria, which gives the proximal tubule a large reabsorption capacity
Loop of Henle / nephron loop:
- descending limb: squamous cells (thin segment)
- ascending limb: cuboidal / columnar cells (thick segment)
Distal convoluted tubule:
- cuboidal cells
- no microvilli
- conveys urine to collecting ducts
Describe the anatomy and function of a collecting duct
- each duct receives filtrate from many nephrons
- passes through medulla for final adjustments to urine concentration and content
- ducts fuse together and deliver urine to minor calyces via renal papilla
Describe a juxtaglomerular apparatus
The region where the distal loop of Henle lies against the afferent (and sometimes efferent) arteriole of glomerulus
What are the 3 types of cells in a juxtaglomerular apparatus?
Macula densa (MD) cells:
- in wall of tubule
- chemoreceptors
- monitor NaCL content of filtrate entering distal convoluted tubule
Juxtaglomerular (JG) cells:
- in arteriolar walls
- mechanoreceptors
- contain granules of renin
Extraglomerular mesangial cells:
- between tubule and arteriole
- regulate MD and JG cells
