Anatomy Terms Starting With K
Anatomy Glossary: K
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Kidney
/ KID-nee / · Old English cwid, womb region (uncertain)
Kidney kidney is a paired bean-shaped organ that filters blood to produce urine, regulates electrolyte balance, controls blood pressure via renin secretion, and produces erythropoietin to stimulate red blood cell production.
Each kidney contains approximately one million nephrons the functional units of filtration, reabsorption, and secretion organized into an outer cortex and inner medulla. The renal artery supplies blood; the renal pelvis collects urine draining via the ureter to the bladder. A single healthy kidney is sufficient for normal life an important fact in living donor transplantation, where 90,000 kidneys are transplanted globally each year.
Human kidneys receive a large share of the blood pumped by the heart even though they are small organs. This heavy blood flow supports filtration and regulation of body chemistry.
Urinary System Fun Facts →Kidneys only remove wastes. Kidneys also regulate water, salts, blood pressure, acid-base balance, and red blood cell production signals.
Circulatory System Fun Facts →Camel kidneys help conserve water by producing concentrated urine. This supports survival in dry environments where water is scarce.
Korotkoff Sounds
/ koh-ROT-koff SOWNDZ / · Named after Nikolai Korotkoff, Russian physician who described them in 1905
Korotkoff sounds are the series of sounds heard through a stethoscope over the brachial artery as a blood pressure cuff is slowly deflated, used to determine systolic and diastolic blood pressure values.
As cuff pressure falls below systolic pressure, blood begins to squeeze through the compressed artery in turbulent jets, producing the first clear tapping sound that marks systolic pressure. The sounds pass through five phases: the initial sharp taps of phase one, the swishing sounds of phase two as blood flows more freely, a louder crisper tapping of phase three, a muffled quality in phase four, and complete disappearance in phase five, which marks diastolic pressure. Turbulent flow and vessel wall vibration produce these sounds; in a fully open artery smooth laminar flow produces no detectable sound.
Accurate auscultation requires correct cuff sizing, proper placement over the brachial artery, a deflation rate of 2 to 3 mmHg per second, and a quiet environment.
Nikolai Korotkoff first described these sounds in a paper of just 281 words presented to the Imperial Military Medical Academy in St. Petersburg in 1905. Despite the brevity of his original report, the technique he described became the global standard for non-invasive blood pressure measurement and remains in routine clinical use more than a century later.
Diastolic pressure corresponds to when the Korotkoff sounds first become muffled. Current guidelines define diastolic pressure as the point where sounds completely disappear, which is phase five, not the muffling of phase four.
In pregnant women during the second trimester, blood pressure often falls due to progesterone-driven vasodilation, and Korotkoff sounds can sometimes be heard all the way down to zero pressure. In these cases clinicians record diastolic pressure at the phase four muffling point rather than disappearance, since true silence may never occur.
Kyphosis
/ ky-FOH-sis / · Greek kyphos, hump-backed
Kyphosis is an exaggerated outward curvature of the thoracic spine that produces a rounded or hunched upper back, resulting from structural changes in the vertebrae, poor posture, or underlying disease.
The thoracic spine normally curves gently outward, but in kyphosis this curvature exceeds 45 to 50 degrees as measured on a lateral X-ray using the Cobb angle method. Postural kyphosis, the most common type, develops from habitual slouching and involves no structural vertebral changes; it is typically flexible and correctable with exercise. Scheuermann kyphosis is a structural form in which the anterior edges of multiple thoracic vertebrae become wedge-shaped during adolescent growth, creating a rigid curve that cannot be corrected by posture alone.
Severe kyphosis can compress the thoracic cage, reducing lung capacity and causing back pain, while in extreme cases it may compromise the spinal cord or nerve roots.
Kyphosis has been documented in ancient skeletal remains; a well-preserved skeleton from a Neolithic burial site in Portugal dated to around 4000 BCE shows clear vertebral wedging consistent with Scheuermann kyphosis, making it one of the oldest identified cases of a named spinal condition in the archaeological record.
Kyphosis and scoliosis are the same condition. Kyphosis is an exaggerated front-to-back curve of the thoracic spine producing a rounded back, while scoliosis is a sideways curve of the spine; they are distinct deformities that can, occur together.
In elderly individuals with severe osteoporosis, the anterior portions of thoracic vertebrae can fracture under normal body weight, causing compression fractures that progressively wedge multiple bones and result in a kyphotic posture, sometimes called a dowager hump, which is more common in postmenopausal women due to accelerated bone density loss.