2,701 articles
2-day CPET
2-day CPET: two maximal cardiopulmonary exercise tests 24 hours apart used to detect post-exertional malaise in ME/CFS and long COVID; meta-analyses support day-2 decline, recent controlled studies question it.
2045 Initiative
2045 Initiative (Россия 2045), transhumanist project founded February 2011 by Russian entrepreneur Dmitry Itskov in Moscow; Avatar A–D roadmap to mind uploading and cybernetic immortality by 2045, disputed by neuroscientists and behind schedule.
5-HT1A receptor
5-HT1A receptor: inhibitory Gi/o-coupled serotonin GPCR acting as raphe autoreceptor and postsynaptic heteroreceptor; target of buspirone, gepirone, vilazodone, and WAY-100635 in anxiety and depression research.
661W
661W is an immortalized mouse cone photoreceptor-like cell line cloned from retinal tumors, the most widely used cell model for retinal disease research, drug screening, and gene therapy development.
Abby and Brittany Hensel
Abby and Brittany Hensel (Abigail and Brittany Lee Hensel, born 1990) are American dicephalic parapagus conjoined twins, two heads on one torso, unseparated, Minnesota teachers; Abby married Josh Bowling in 2021.
Abdomen
The abdomen is the anterior region of the trunk between the diaphragm and the pelvic brim, housing most organs of the digestive, urinary, endocrine, and circulatory systems.
Abdominal and pelvic lymph nodes
The abdominal and pelvic lymph nodes are regional node groups that drain the abdominal organs and pelvic viscera, arranged along the aorta, iliac, and mesenteric arteries.
Abdominal aorta
Abdominal aorta: the aortic segment from the diaphragm to the bifurcation into the common iliac arteries at about L4. Gives paired, unpaired, and terminal branches; aneurysm is dilation to 3 cm or more.
Abdominal cavity
The abdominal cavity is the body space from diaphragm to pelvic inlet holding the digestive organs, lined by the peritoneum; distinct from the peritoneal cavity, subdivided into quadrants, and clinically linked to peritonitis and hernias.
Abdominal external oblique muscle
Abdominal external oblique muscle (musculus obliquus externus abdominis): largest, most superficial of the three flat anterolateral abdominal wall muscles; originates ribs 5-12, inserts linea alba, pubic tubercle, iliac crest; forms inguinal ligament; flexes, rotates trunk, aids forced expiration.
Abdominal hair
Abdominal hair, also called belly or stomach hair, is androgen-dependent terminal hair on the human abdomen; prominent growth in women defines part of hirsutism (mFG score 4-6), and abdominal hair transports navel lint.
Abdominal Reflex
Abdominal reflex: superficial cutaneous reflex (T6-T12) in which stroking the abdominal wall contracts the abdominal muscles, pulling the umbilicus toward the stimulus; absent in about 20% of normal people, lost with thoracic cord or corticospinal tract lesions.
Abdominal wall
Abdominal wall: the skin, fascia, muscle, and peritoneum enclosing the abdominal cavity; anterolateral and posterior walls, intra-abdominal pressure biomechanics, hernia repair, and abdominal wall reconstruction.
Abdominojugular test
Abdominojugular test (hepatojugular reflux): bedside maneuver of sustained abdominal compression while watching the jugular vein; sustained >3 cm rise signals right heart failure. Described by Pasteur in 1885; not a reflex.
Abducens nerve
The abducens nerve (CN VI), also called the sixth cranial nerve, is a purely motor cranial nerve from the pons that supplies the lateral rectus muscle, abducting the eye.
Abnormal neuronal migration
Abnormal neuronal migration (ICD-11 LA05.5, neuronal migration disorders): failure of fetal neurons to reach correct cortical positions, causing lissencephaly, heterotopia, polymicrogyria, and cortical dysplasia with epilepsy; key genes LIS1, DCX, FLNA, TUBA1A.
Abnormal posturing
Abnormal posturing: decorticate (flexor) and decerebrate (extensor) reflex postures in coma, first described by Sherrington in 1898, scored on the GCS motor scale, indicating severe brain or brainstem injury with poor survival.
Abscess of spleen
Abscess of spleen (splenic abscess, ICD-11 3B81.71): a rare pus-forming infection of the spleen, incidence 0.1–0.7%, usually from hematogenous spread; treated with antibiotics, percutaneous drainage, or splenectomy.
Abscess of thymus
Abscess of thymus (suppuration of thymus), ICD-11 4B40.1 and ICD-10-CM E32.1, is a rare pus-forming infection of the thymus, seen in neonates, immunocompromised patients, or from adjacent infection, diagnosed by CT or MRI.
Absence of innominate vein
Absence of innominate vein is a rare congenital anomaly in which the left brachiocephalic vein is absent, usually asymptomatic and typically found incidentally on imaging or during surgery.
Accessory nerve
Accessory nerve (CN XI, spinal accessory nerve), a mostly motor cranial nerve named for Thomas Willis, innervates the sternocleidomastoid and trapezius, exits via the jugular foramen, and is injured mainly during neck surgery, causing shoulder dysfunction.
Accessory pathway
Accessory pathway: an abnormal atrioventricular muscle bridge bypassing the AV node, causing pre-excitation (WPW pattern), AVRT, and risk of pre-excited AF; risk-stratified by EP study and cured by catheter ablation.
Accessory rib
Accessory rib (supernumerary rib), most often the cervical rib from C7, also lumbar or intrathoracic; congenital extra rib, prevalence about 1%, can cause thoracic outlet syndrome.
Accessory spleen
Accessory spleen (splenunculus, splenule): congenital ectopic splenic tissue, distinct from splenosis. Present in about 14.5% of people, usually near the splenic hilum; can cause hematologic recurrence after splenectomy and mimic tumors on imaging.
Accessory tricuspid valve tissue
Accessory tricuspid valve tissue (ORPHA:95462, ICD-10 Q22.8) is a rare congenital tricuspid valve malformation, usually with other congenital heart defects, causing murmurs, dyspnea, cyanosis, or outflow obstruction; treated by surgical excision.
Accommodation reflex
Accommodation reflex (near response, near triad): a three-part reflex for near vision, lens thickening via ciliary muscle, pupillary constriction, and convergence, mediated by the Edinger-Westphal nucleus, oculomotor nerve, and ciliary ganglion.
Acetabulum
The acetabulum, or cotyloid cavity, is the cup-shaped socket of the hip bone, formed where the ilium, ischium, and pubis meet, that holds the femoral head in the hip joint.
Acetylcholine
Acetylcholine (ACh), the first neurotransmitter identified, is a choline ester acting at nicotinic ion-channel and muscarinic GPCR receptors in CNS, autonomic, and neuromuscular synapses; degraded by acetylcholinesterase; central to Alzheimer's and schizophrenia drug development.
Acetylcholine receptor
Acetylcholine receptor: cell-surface proteins activated by acetylcholine, divided into ionotropic nicotinic and G-protein-coupled muscarinic (M1-M5) receptors; targets of nicotine, myasthenia gravis antibodies, and the 2024 antipsychotic KarXT.
Achilles tendon
Achilles tendon, or calcaneal tendon (tendo calcaneus), the thickest tendon, connecting calf muscles to the heel bone; named by Verheyen in 1693; rupture treated operatively or nonoperatively with differing re-rupture and complication rates.