Nursing HAP201 Chapter Notes - Chapter 26: Natriuretic Peptide, Skeletal Muscle, Fibrinogen
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HAP201 Week Ten/Chapter 26: The Urinary System
26.1: Overview of Kidney Functions
• There are eight functions of the kidneys
o Regulation of blood ionic composition: they regulate the blood levels of several ions, e.g. sodium, potassium, calcium, chloride, and
o Regulation of blood pH: they excrete a variable amount of hydrogen ions into the urine and conserve bicarbonate ions (HCO3-), which
are an important buffer of H+ in the blood.
o Regulation of blood volume: they adjust blood volume by conserving or eliminating water in the urine. This will then cause in increase in
BP and vice-versa
o Regulation of blood pressure: they regulate BP by secreting renin to activate the renin-angiotensin-aldosterone pathway. Increased renin
o Maintenance of blood osmolarity: by separating regulating loss of water and loss of solutes in the urine, the kidneys maintain a
relatively constant blood osmolarity
o Production of hormones: they produce two hormones. Calcitriol, the active form of vitamin D which regulates calcium homeostasis and
erythropoietin, which stimulates the production of red blood cells
o Regulation of blood glucose level: they can use the amino acid glutamine in gluconeogenesis, the synthesis of new glucose molecule.
They can release glucose into the blood to help maintain a normal blood glucose level
o Excretion of wastes and foreign substances: urine helps excrete wastes – substances that have no useful function in the body. Some
wastes excreted by urine result from metabolic reactions in the body.
26.2: Anatomy and Histology of the Kidneys
• The kidneys are located between the levels of the last thoracic and third lumbar vertebrae, so they are protected by ribs 11 and 12. If these ribs
are fractured, they can puncture the kidneys and cause significant damage.
• The right kidney is slightly lower than the left, as the liver occupies considerable space on the right side superior to the kidney
• External Anatomy of the Kidneys
o Near the centre of the concave border is an indentation called the renal hilum, through which the ureter emerges from the kidney along
with blood vessels, lymphatic vessels, and nerves.
o There are three layers of tissue that surround the kidney.
▪ Renal capsule: this is the deep, smooth and transparent layer of dense irregular connective tissue that is continuous with the outer
coat of the ureter. It is a barrier against trauma and helps maintain the shape.
▪ Adipose capsule: this is the middle layer which is a mass of fatty tissue surrounding the renal capsule. It protects kidneys from
trauma and holds them in place in the abdominal cavity.
▪ Renal fascia: this is the superficial, thin layer of dense irregular connective tissue that anchors the kidney to the surrounding
structures and to the abdominal wall. On the anterior surface of the kidneys, the renal fascia is deep to the peritoneum
• Internal Anatomy of the Kidneys
o There are two distinct regions in the kidney
▪ Renal cortex: this is a superficial, light red region. It is smooth-textured extending from the renal capsule to the bases of the renal
pyramids and into the spaces between them. It is divided into an outer cortical zone and an inner juxtamedullary zone. The portions
of the cortex that extend between the renal pyramids are called renal columns
▪ Renal medulla: this is a deep, darker reddish-brown inner region that consists of several cone-shaped renal pyramids. The base of
each pyramid faces the renal cortex and its apex, called renal papilla, points towards the renal hilum.
o Together, the renal cortex and renal pyramids of the renal medulla constitute the parenchyma or functional portion of the kidney. Within
the parenchyma are nephrons.
o Nephrons create filtrate (filtered fluid) which drains into papillary ducts that extend through the renal papillae of the pyramids.
o These ducts drain into minor (8-10) and major (2-3) calyces. A minor receives urine from the papillary ducts of one renal papilla and
delivers it to a major calyx. Once the filtrate enters the calyces, it becomes urine since no further reabsorption can occur. From the major
calyces, urine drains into a single large cavity called the renal pelvis and then out through the ureter to the urinary bladder.
o The hilum expands into a cavity called the renal sinus, which contains part of the renal pelvis, the calyces, and branches of the renal blood
vessels and nerves. Adipose tissue helps stabilize the position of these structures in the renal sinus
• Blood and Nerve Supply of the Kidneys
o The kidneys receive 20-25% of the resting cardiac output via the right and left renal arteries.
o Within the kidney, the renal artery divides into several segmental arteries, which supply different areas of the kidney. Each gives off
several branches that enter the parenchyma and pass through the renal columns between the renal lobes as the interlobar arteries
o A renal lobe contains a renal pyramid, some of the renal column on either side of the pyramid, and the renal cortex at the base of the
o At the base, the interlobar arteries become the arcuate arteries. Divisions of these arteries produce a series of cortical radiate arteries.
These arteries radiate outward and enter the renal cortex where they branch off becoming afferent arterioles.
o Each nephron receives one afferent arteriole, which divides into the glomerulus.
o The glomerulus capillaries reunite to form an efferent arteriole that carries blood out of the glomerulus. These capillaries are positioned
between two arterioles, rather than between an arteriole and a venule
o The efferent arteriole divides into the peritubular capillaries, which surround tubular parts of the nephron in the renal cortex. These
capillaries eventual unite to form cortical radiate veins, which also receive blood from the vasa recta (some capillaries that extend from
o The blood the drains through arcuate veins to the interlobar veins running between renal pyramids
o Blood will eventually leave the kidneys through a single renal vein that exists at the renal hilum and carries venous blood to the inferior
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