2,701 articles
Penis
Penis: the male external copulatory and urinary organ, made of two corpora cavernosa and a corpus spongiosum around the urethra. Erection is nitric-oxide-mediated blood engorgement; key conditions include ED, Peyronie's disease, and priapism.
Peptide hormone
Peptide hormone: amino-acid-chain hormones (insulin, GLP-1s, secretin, oxytocin) acting via cell-surface receptors; made as preprohormones, short half-life, distinct from steroid hormones; basis of approved drugs and unapproved wellness peptides.
Peptidergic neuron
Peptidergic neuron (Cell Ontology CL:0000110): a neuron using neuropeptides as transmitters, stored in large dense-core vesicles, acting on GPCRs, usually co-released with classical transmitters.
Perception
Perception is the process by which the nervous system computes over sensory inputs to build models of the world, from receptor transduction through multisensory integration and predictive inference.
Percutaneous coronary intervention
Percutaneous coronary intervention (PCI), or coronary angioplasty, is a catheter-based procedure opening blocked coronary arteries with balloon and stent; introduced by Grüntzig in 1977, drug-eluting stents are its standard, with CABG favored in complex disease.
Percutaneous intentional extraluminal revascularization
Percutaneous intentional extraluminal revascularization (PIER, subintimal angioplasty) is an endovascular technique for chronic total occlusions of peripheral arteries, creating a subintimal dissection channel with true-lumen reentry; technical success 65-100%, used when intraluminal crossing fails.
Perfluorohexyloctane
Perfluorohexyloctane (F6H8) is a chemically inert semifluorinated alkane used in prescription eye drops for dry eye disease, marketed as MIEBO in the United States since 2023.
Perforated eardrum
Perforated eardrum (tympanic membrane perforation): a hole or tear in the eardrum from infection, injury, loud noise, or pressure change; usually heals within weeks to two months, with myringoplasty for persistent holes.
Perfusion
Perfusion is blood flow through tissue vessels, delivering oxygen and removing carbon dioxide, quantified as ml/min/g. Covers its history (Harvey, Malpighi), autoregulation, bedside and laboratory assessment in shock, and optical, fluorescence, and imaging measurement techniques.
Perfusionist
Perfusionist: allied health professional who operates the heart-lung machine (cardiopulmonary bypass) during cardiac surgery and runs ECMO and mechanical support; credentialed as CCP by the ABCP (est. 1975), with state licensure in Massachusetts, Maryland, and Texas.
Periaortic lymph nodes
Periaortic (para-aortic, lumbar) lymph nodes: retroperitoneal nodes along the aorta and IVC draining kidney, adrenal, gonads, and uterine corpus; seven imaging subgroups; PET-CT is the most accurate metastasis test.
Pericardium
The pericardium, also known as the pericardial sac or heart sac, is the double-layered fibrous sac enclosing the heart, lubricating its movement and anchoring it within the chest.
Perichondritis of external ear
Perichondritis of external ear (ICD-11 AA04; ICD-10 H61.0) is infection of the perichondrium around outer-ear cartilage, usually after cartilage piercing or trauma, most often caused by Pseudomonas aeruginosa, risking cauliflower ear.
Pericyte
Pericytes are mural cells embedded in the basement membrane of capillaries and microvessels, wrapping endothelial cells. Also called Rouget cells; they regulate blood flow, angiogenesis, and the blood-brain barrier, and lack a single specific marker.
Perifoveal exudative vascular anomalous complex
Perifoveal exudative vascular anomalous complex (PEVAC, also PVAC) is a rare idiopathic large aneurysmal lesion of the deep retinal capillary plexus near the fovea, diagnosed by exclusion, poorly responsive to anti-VEGF, distinct from type 3 MNV and MacTel.
Periglomerular cell
Periglomerular cell (PG cell, juxtaglomerular interneuron): small GABAergic interneuron surrounding olfactory bulb glomeruli, soma 5–10 µm, uniglomerular dendrites, dendrodendritic inhibition of mitral/tufted cells, dopaminergic TH+ subtype, adult-born, distinct from renal periglomerular usage.
Perinatal asphyxia
Perinatal asphyxia (birth asphyxia) is hypoxic-ischemic organ injury near delivery, causing about 900,000 neonatal deaths yearly; its brain form is HIE, treated with 72-hour therapeutic hypothermia at 33.5–34.5 °C.
Perineum
The perineum, or anogenital area, is the body region between the thighs containing the external genitalia and anal opening, a region important in obstetrics and surgery.
Perioperative tachyarrhythmia
Perioperative tachyarrhythmia is a rapid heart rhythm, above 100 beats per minute, arising during or after surgery and anesthesia; atrial fibrillation accounts for about 90% of cases.
Periorbital cellulitis
Periorbital (preseptal) cellulitis: bacterial infection of the eyelid and surrounding skin anterior to the orbital septum, distinct from orbital cellulitis; normal vision and eye movement, treated with oral or IV antibiotics.
Periorbital puffiness
Periorbital puffiness, or periorbital edema (bags under the eyes), is swelling around the eye orbit from fluid, fat or inflammation; causes range from aging, salt, sleep loss and allergies to cellulitis, thyroid or renal disease.
Peripartum cardiomyopathy
Peripartum cardiomyopathy (PPCM), or postpartum cardiomyopathy, is heart failure with LVEF under 45% arising late in pregnancy or within five months after delivery, with no other cause; incidence about 1 in 2000 births, highest in Nigeria.
Peripartum Period
Peripartum period: the time shortly before, during, and immediately after childbirth (MeSH D058725). Also called peri-partum; distinct from postpartum (mother) and postnatal (baby), with definitions ranging from delivery to 28 days after, or conception to one year postpartum.
Peripheral and visceral arteriovenous malformation
A peripheral or visceral arteriovenous malformation is a congenital tangle of abnormal blood vessels outside the brain and spinal cord, where arteries connect directly to veins.
Peripheral artery disease
Peripheral artery disease (PAD), or peripheral arterial disease, is atherosclerotic narrowing of leg arteries causing claudication, ischemia, and amputation risk; diagnosed by ankle-brachial index, treated with exercise, antithrombotics, and revascularization.
Peripheral vision
Peripheral vision is sight outside the fovea, covering about 99.9% of the visual field. Also called indirect or eccentric vision, it is limited mainly by crowding, not blur, and excels at motion and scene gist.
Peripherally inserted central catheter
Peripherally inserted central catheter (PICC): central venous catheter inserted via an arm vein with tip in the lower SVC or cavoatrial junction; first described 1975, used for antibiotics, nutrition, chemotherapy; key risks are bloodstream infection and thrombosis.
Peristalsis
Peristalsis: involuntary wave-like contraction and relaxation of digestive tract muscles propelling contents from pharynx to anus; includes esophageal waves, the fasting migrating motor complex, and disorders such as achalasia and gastroparesis.
Peritubular capillaries
Peritubular capillaries are tiny fenestrated blood vessels in the kidney cortex that surround the renal tubules, take up reabsorbed water and solutes, and supply tubular cells with oxygen.
Periventricular leukomalacia
Periventricular leukomalacia (PVL), also called encephalopathy of prematurity, is white matter death around the brain ventricles in premature infants, caused by ischemia and infection, diagnosed by ultrasound or MRI, and strongly linked to cerebral palsy.