Human Anatomy: The Abdomen and The Thorax

Comprehensive vocabulary flashcards covering the anatomical structures, boundaries, vascular supply, muscular layers, and physiological systems of both the abdomen and thorax.

Peritoneal Cavity

A single large abdominal cavity continuous with the pelvic cavity, enclosed by the abdominal wall; structures within it are either suspended by mesenteries or positioned between the peritoneum and the musculoskeletal wall.

Active / Forced Expiration

The respiratory phase driven by the contraction of abdominal muscles; contracting these same muscles while closing the airways also generates pressure for urination, defecation, and pushing during labor.

Inferior Thoracic Aperture (Abdominal Boundary)

The superior boundary of the abdomen sealed off by the diaphragm, bordered by vertebra $T12$, ribs $11$ and $12$, the costal cartilages of ribs $7$ through $10$, and the xiphoid process.

Pelvic Inlet

The inferior boundary of the abdomen, bordered posteriorly by the sacrum, anteriorly by the pubic symphysis, and laterally by the rim of the pelvic bones.

Inguinal Canal

A ligamentous ring and passage through the lower abdominal wall that transmits the ilio-inguinal nerve in both sexes, the spermatic cord and genital nerve branch in males, and the round ligament of the uterus in females.

Celiac Trunk

The anterior branch of the abdominal aorta that branches immediately inferior to the diaphragm to supply the organs of the embryonic foregut, including the stomach, spleen, and liver.

Superior Mesenteric Artery

An anterior branch of the abdominal aorta that supplies blood to the embryonic midgut, including the small intestine, ascending colon, and transverse colon.

Inferior Mesenteric Artery

An anterior branch of the abdominal aorta that supplies blood to the embryonic hindgut, specifically the descending colon and rectum.

Hepatic Portal Vein

A large vascular trunk formed by veins draining the gastrointestinal tract that directs nutrient- and toxin-rich venous blood into the liver for screening and metabolic processing prior to entering systemic circulation.

Linea Alba

A tough central fibrous band and midline aponeurotic seam where the bilateral abdominal wall muscle sheets intersect.

Lacunar Ligament

A ligament that secures the inferior border of the external oblique aponeurosis to the pubis; it is continuous with the inguinal and pectineal ligaments.

Transversus Abdominis

The deepest muscle layer of the anterolateral abdominal wall whose horizontal fibers run below the plane of the ribs to compress abdominal contents.

Pyramidalis Muscle

A small muscle located anteriorly in the lower abdominal wall that functions as a synergist to tense the linea alba.

Greater Omentum

A large, highly vascular, four-layered sheet of peritoneal mesentery loaded with fat that drapes over the lower abdominal viscera from the greater curvature of the stomach.

Lesser Omentum

A double layer of peritoneum composed of the hepatogastric and hepatoduodenal ligaments that anchors the liver to the lesser curvature of the stomach and duodenum.

Omental Bursa

The peritoneal subdivision (lesser sac) situated posterior to the stomach, lesser omentum, and liver that connects to the greater sac via the omental (epiploic) foramen.

Pyloric Sphincter

A thickened ring of gastric smooth muscle at the junction of the stomach pylorus and duodenum that regulates the exit of acidic chyme.

Duodenojejunal Flexure

The junction where the retroperitoneal duodenum transitions into the intraperitoneal jejunum, suspended and supported by a suspensory ligament.

Appendix

A tubular lymphoid diverticulum arising at the ileocecal junction of the cecum that possesses active immune functions and acts as a bacterial reservoir.

Vasa Recta

Straight arterial branches arising from the arterial arcades in the mesentery that provide terminal perfusion directly into the wall of the jejunum and ileum.

Quadrate Lobe

An anatomical lobe situated on the visceral surface of the liver, positioned anteriorly between the gallbladder and the fissure for ligamentum teres, that functions functionally with the left lobe.

Caudate Lobe

An independent, functionally distinct anatomical lobe of the liver situated posteriorly between the inferior vena cava and the fissure for ligamentum venosum.

Islets of Langerhans

Endocrine cellular microclusters in the pancreas containing alpha cells (secreting glucagon), beta cells (secreting insulin and amylin), and D cells (secreting somatostatin).

Spleen

A lymphoid visceral organ situated in the left upper abdominal quadrant that destroys damaged red blood cells and functions as a blood reservoir to rapidly adjust hematocrit.

Renal Medulla

The deep, pyramid-containing tissue layer of the kidney where collecting tubules funnel urine through the renal papillae into minor calyces, major calyces, and the renal pelvis.

Suprarenal Glands

Paired endocrine organs resting on the superior poles of the kidneys that produce catecholamines and glucocorticoids.

Ureteric Constrictions

The three anatomical narrowing sites along the ureter prone to kidney stone impaction: the ureteropelvic junction, the crossing of the pelvic inlet, and the entrance into the urinary bladder.

Superior Thoracic Aperture

The bony thoracic inlet bounded by vertebra $T1$, the first pair of ribs, and the superior edge of the sternal manubrium, transmitting major vessels, nerves, the trachea, and the esophagus.

Mediastinum

The central tissue partition within the thoracic cavity separating the right and left pleural cavities, divided into superior and inferior compartments by a transverse plane through the sternal angle and the $T4/T5$ intervertebral disc.

Pleural Cavities

Paired potential spaces enclosing the lungs between the outer parietal pleura (lining the thoracic wall) and inner visceral pleura (coating lung tissue), containing serous fluid to maintain lung expansion.

Pneumothorax

A clinical condition resulting from air entering the pleural space following a chest wall or pleural puncture, destroying the negative surface tension and leading to lung collapse.

Retromammary Space

A layer of loose connective tissue separating the posterior base of the mammary gland from the deep pectoral fascia, permitting free breast mobility.

Lactiferous Ducts

A group of $15\text{--}20$ distinct tubular excretory conduits in each breast that drain secretory lobules and independently open at the tip of the nipple.

Pectoralis Major

A large superficial chest muscle responsible for adduction, medial rotation, and flexion of the humerus.

Subclavius

A small anterior chest muscle situated beneath the clavicle that pulls the clavicle medially and depresses the tip of the shoulder.

Pectoralis Minor

A thin, deep muscular component of the pectoral wall that depresses the tip of the shoulder and protracts the scapula.

Costal Groove

A longitudinal channel located along the inferior internal surface of each rib that accommodates and protects the intercostal vein, artery, and nerve.

True Ribs

Rib pairs $1$ through $7$, which articulate directly with the sternum via their own individual costal cartilages.

False Ribs

Rib pairs $8$ through $12$, consisting of three pairs ($8\text{--}10$) whose costal cartilages merge into the rib above, and two pairs ($11\text{--}12$) called floating ribs with unattached anterior ends.

Costovertebral Joints

Synovial joints of the thoracic wall consisting of two synovial compartments where the rib head articulates with vertebral bodies, and a costotransverse joint where the rib tubercle articulates with the transverse process.

External Intercostal Muscles

The most superficial muscle layer in the intercostal spaces whose primary contraction elevates the ribs during inspiration.

Internal Intercostal Muscles

The intermediate muscle layer residing between adjacent ribs whose contraction depresses the rib cage during active expiration.

Azygos Vein

A major unilateral venous conduit running on the right side of the posterior thoracic wall that collects blood from intercostal veins and drains directly into the superior vena cava.

Hemiazygos Vein

A left-sided posterior thoracic vein that receives drainage from the lower intercostal spaces and abdomen before shunting blood across the vertebral column into the azygos vein.

Phrenic Nerves

Nerves arising from spinal segments $C3\text{--}C5$ (predominantly $C4$) that provide motor and sensory innervation to the diaphragm, as well as sensory innervation to the pericardium and mediastinum.

Oblique Fissure

A deep pulmonary fissure extending to the hilum present in both lungs; it separates the inferior lobe from the superior and middle lobes in the right lung, and the inferior lobe from the superior lobe in the left lung.

Horizontal Fissure

A transverse pulmonary cleft found uniquely on the right lung that separates the middle lobe from the superior lobe.

Pericardium

A fibroserous sac encasing the heart and the roots of the great vessels, composed of an external fibrous pericardium and an inner serous pericardium consisting of parietal and visceral (epicardium) layers.

Chordae Tendineae

Fibrous collagenous cords connecting ventricular papillary muscles to the free margins of the atrioventricular valve cusps, preventing valve eversion during ventricular systole.

Isovolumic Ventricular Contraction

The early phase of ventricular systole where rising chamber pressure forces the atrioventricular valves closed before pressure exceeds arterial resistance to open the semilunar valves.

Isovolumic Ventricular Relaxation

The initial period of ventricular diastole where relaxing myocardium leads to a drop in chamber pressure, snapping semilunar valves closed before atrioventricular valves open.

Sinoatrial (SA) Node

The primary intrinsic pacemaker of the heart situated in the right atrium that depolarizes the atrial walls and sets normal heartbeat frequency at approximately $70\,\text{bpm}$.

Atrioventricular (AV) Node

An electrical conduction station that introduces a $0.5\,\text{sec}$ delay to coordinate atrial and ventricular contractions; it can act as a secondary pacemaker at approximately $50\,\text{bpm}$.

Purkinje Fibers

Specialized conducting myocardial fibers that rapidly distribute electrical depolarization upward through the outer ventricular walls to ensure apex-to-base ventricular ejection.

Ligamentum Arteriosum

A fibrous connective tissue cord in the superior mediastinum connecting the pulmonary trunk to the aortic arch; represents the anatomical remnant of the fetal ductus arteriosus.

Thymus

A superior mediastinal lymphoid organ serving as the site of lymphocyte maturation and training, which undergoes regression and is markedly reduced or absent in adults.