21.2: Kidneys
- Page ID
- 53831
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Kidneys
There are two kidneys, one right and one left. They are retroperitoneal (posterior to peritoneum) and encased in protective layers of adipose tissue along the posterior body wall of the abdomen.
Above: Position of the kidneys. The kidneys are surrounded by perinephric fat and surrounded by an anterior renal fascia and posterior renal fascia.
The kidneys filter dissolved materials from the blood, including metabolic wastes, regulate electrolytes, regulate fluid volume (thereby influencing blood pressure), concentrates and stores waste products in the form of urine, and reabsorbs metabolically important substances back into the circulatory system. The following are specific functions of the kidneys:
- Remove waste: The kidneys filter waste products and excess fluid out of the blood and remove them from the body in the form of urine. (nitrogenous wastes such as urea and ammonium)
- Maintain the right balance of chemicals in the body: The kidneys keep the right balance of chemicals, such as sodium, potassium, calcium, magnesium, and other substances your body needs to function properly. They filter excess amounts of these chemicals from the blood and get rid of them in the urine.
- Synthesize several regulatory chemicals: The kidneys produce and secrete three important chemicals: renin, erythropoietin, and the active form of vitamin D (Calcitriol).
Above: Anatomy of a kidney. Left kidney shown with frontal section.
|
Kidney Structure |
Location |
Function |
|---|---|---|
|
columns (renal) |
tissue-filled areas between the pyramids |
anchor the medulla to the cortex and provide a place for blood vessels to travel |
|
cortex (renal) |
a region of the kidney where nephrons are mostly located |
region of the kidney where blood is filtered and urine is formed; contain nephrons |
|
fibrous capsule |
fibrous layer on the lining the outside of the kidney |
Protects and supports the kidney |
|
glomerulus |
microscopic bundle of capillaries in the cortex of the kidney; part of a nephron |
high-pressure leaky capillaries create raw filtrate (fluid that will become urine); fluid and solutes are pushed out of these capillaries from the blood and into the Bowman's capsule / glomerular capsule |
|
hilum |
a central, medial fissure in the kidney |
location where ureters, blood vessels, and nerves enter the kidney |
|
major calyx |
large divisions of the renal pelvis; where minor calyces fuse together |
collects urine from the minor calyces and transfer it to the renal pelvis |
|
minor calyx |
smaller divisions of the major calyces; between major calyces and renal papillae |
collects urine from the renal papillae and transfers it to the major calyces |
|
medulla (renal) |
a region of the kidney between the cortex and the minor calyces |
contain nephron loops of juxtamedullary nephrons; balancing water and salt concentrations in the blood |
|
nephron |
microscopic structures mostly found in the renal cortex, but some components found in the medulla; composed of kidney tubules |
filters the blood to remove wastes and fluid; produces urine |
|
papilla (renal) |
between the pyramids and the minor calyces |
collects urine from the collecting ducts and transfers to the minor calyces |
|
pyramids (renal) |
triangular-shaped regions of the medulla |
transfer of urine from nephrons to the calyces |
|
renal pelvis |
between the major calyces and the ureter |
collects urine from the major calyces and transfers it to the ureter |
Above: Cadaver kidney (left) right kidney, unsectioned and (right) kidney, frontal sectioned.
Above: Microscopic image of kidney tissue, magnified by 10x.
In order for the kidney to work properly, blood vessels must carry blood to the glomerulus for filtration, then to the peritubular capillaries to drop off oxygen (and pick up carbon dioxide and reabsorb water and electrolytes), and then to the renal vein to head back to the heart. Below are the vessels that make this special circulation happen. They are listed in the order that blood flows through them.
- descending abdominal aorta
- renal artery
- segmental artery
- interlobar artery
- arcuate artery
- cortical radiate artery
- afferent arteriole
- glomerulus
- efferent arteriole
- peritubular capillary
- cortical radiate vein
- arcuate vein
- interlobar vein
- segmental vein
- renal vein
- inferior vena cava