Cardiovascular, Immune, and Digestive Systems Review

Comprehensive vocabulary flashcards covering the cardiovascular system, immune system and lymphoid organs, digestive tract anatomy, histology, and accessory digestive glands.

Auricle

An ear-like pouch extending from the atrium that functions to increase total atrial volume.

Pectinate Muscles

Prominent parallel muscular ridges located along the atrial walls that aid in atrial contraction.

Fossa Ovalis

An oval depression located on the interatrial septum of the right atrium that represents the remnant of the fetal foramen ovale.

Diastole

The cardiac cycle phase of ventricular relaxation and filling, during which the atrioventricular (AV) valves open and ventricles receive blood.

Systole

The cardiac cycle phase of ventricular contraction and ejection, during which the AV valves close and blood is pumped through the semilunar valves.

First Heart Sound ($S_1$)

The "lub" sound caused by the closure of the atrioventricular (tricuspid and mitral) valves at the onset of ventricular systole.

Second Heart Sound ($S_2$)

The "dub" sound caused by the closure of the semilunar (aortic and pulmonary) valves at the beginning of ventricular diastole.

Chordae Tendineae

Fibrous, tendon-like cords that connect the cusps of the atrioventricular valves to papillary muscles, preventing valve prolapse and regurgitation during ventricular systole.

Azygos Vein

A venous channel draining the right thoracic wall and intercostal spaces that empties into the superior vena cava, serving as a collateral pathway between the superior and inferior venae cavae.

Brachiocephalic Trunk

The first and largest branch arising from the arch of the aorta (on the right side only), which bifurcates into the right common carotid artery and the right subclavian artery.

Left Anterior Descending (LAD) Artery

A critical coronary artery branch that supplies the anterior left ventricle and interventricular septum; occlusion of this artery frequently leads to fatal myocardial infarction.

Aortic Sinuses

Anatomical pockets located immediately behind the aortic valve cusps that house the openings for the coronary arteries, filling with backflowing blood during diastole.

Sinoatrial (SA) Node

The physiological pacemaker of the heart, located at the junction of the superior vena cava and the right atrium, which establishes the intrinsic heart rate at approximately $60\text{--}100\text{ bpm}$.

Atrioventricular (AV) Node

Specialized conducting tissue within the interatrial septum that introduces an approximate $0.1\text{ s}$ delay in electrical conduction to allow complete atrial emptying and ventricular filling.

Purkinje Fibers

Specialized modified cardiac conducting cells situated in the subendocardial layer that rapidly propagate electrical impulses throughout the ventricular myocardium to trigger contraction.

Baroreceptors

Mechanoreceptors located in the aortic arch, carotid sinus, pulmonary vessels, and atria that detect arterial and venous stretch to regulate systemic blood pressure.

Cardiac Tamponade

A pathological state in which blood or fluid fills the pericardial sac, compressing the heart chambers, inhibiting ventricular filling, and precipitating hypotension, jugular venous distension, and shock.

Thoracic Duct

The major lymphatic vessel that collects lymph from the lower extremities, abdomen, left thorax, left upper limb, and left head and neck, discharging into the left subclavian vein.

Antigen-Presenting Cells (APCs)

Immune cells—including macrophages, dendritic cells (e.g., Langerhans cells), and B lymphocytes—that process foreign antigens and present them on MHC II molecules to activate helper T cells ($CD4^+$).

Natural Killer (NK) Cells

Innate cytotoxic lymphocytes that destroy virus-infected, cancerous, and foreign cells directly without requiring prior antigen sensitization or presentation via MHC molecules.

Innate Immune Response

The rapid, nonspecific primary line of defense that activates within minutes to hours, utilizing barriers, complement, and cells like neutrophils, macrophages, mast cells, and NK cells without immunologic memory.

Adaptive Immune Response

A delayed, antigen-specific immune mechanism mediated by B and T lymphocytes that mounts targeted humoral or cell-mediated responses and produces long-term immunological memory.

Major Histocompatibility Complex Class I (MHC I)

Cell-surface glycoproteins expressed on all nucleated cells that present endogenous antigens (e.g., viral or tumor proteins) to cytotoxic T lymphocytes ($CD8^+$).

Major Histocompatibility Complex Class II (MHC II)

Cell-surface glycoproteins found exclusively on professional antigen-presenting cells that display exogenous engulfed antigens to helper T lymphocytes ($CD4^+$).

Thymic Involution

The progressive age-dependent shrinkage and loss of functional lymphatic tissue in the thymus gland, leading to reduced production of naive T lymphocytes in older individuals.

Hassall's Corpuscles

Concentric aggregates of degenerating, keratinized thymic epithelial cells (TECs) characteristic of the thymic medulla.

Mucosa-Associated Lymphoid Tissue (MALT)

Non-encapsulated aggregates of lymphoid tissue containing B cells, T cells, dendritic cells, and IgA-secreting plasma cells situated in mucosal membranes exposed to the external environment.

Peyer's Patches

Aggregated lymphoid nodules embedded within the submucosa and mucosa of the small intestine, localized predominantly within the ileum.

White Pulp

The splenic compartment organized around central arterioles, composed of the periarteriolar lymphoid sheath (PALS; T cells) and lymphoid follicles (B cells), responsible for immune surveillance of blood-borne antigens.

Puborectalis Muscle

A muscular sling of the pelvic diaphragm that maintains an approximate $80^\bullet$ anorectal angle to preserve fecal continence, which must relax to allow defecation.

Lower Esophageal Sphincter (LES)

A functional smooth muscle valve located at the cardiac orifice that regulates passage into the stomach and prevents acidic gastric contents from refluxing into the esophagus.

Teniae Coli

Three distinct longitudinal ribbons of smooth muscle running along the exterior of the colon that contract to create pouch-like sacculations known as haustra.

Meissner's (Submucosal) Plexus

An autonomic nerve network located within the submucosa of the GI tract that regulates mucosal glandular secretion, blood flow, and local muscularis mucosae activity.

Auerbach's (Myenteric) Plexus

An enteric nerve network positioned between the inner circular and outer longitudinal smooth muscle layers of the muscularis externa that orchestrates gastrointestinal motility and peristalsis.

Parietal Cells

Gastric epithelial cells located in the gastric glands that synthesize and secrete hydrochloric acid ($HCl$) and intrinsic factor.

Chief Cells

Basophilic gastric gland cells that synthesize and secrete pepsinogen (the inactive precursor to pepsin) and gastric lipase.

Paneth Cells

Specialized secretory cells situated at the base of the intestinal crypts of Lieberkôhn that release antimicrobial agents, including lysozyme and defensins.

Secretin

A hormone produced by duodenal enteroendocrine cells in response to acidic chyme that stimulates pancreatic ductal cells to secrete water and bicarbonate ($HCO_3^-$).

Cholecystokinin (CCK)

An enteroendocrine hormone secreted by the small intestine that induces gallbladder contraction and stimulates pancreatic acinar cells to secrete digestive enzymes.

Portal-Systemic Anastomoses

Vascular connections between the hepatic portal system and systemic venous circulations (located at the esophagus, rectum, and umbilicus) that can dilate into varices under portal hypertension.

Parotid Gland

The largest paired salivary gland, containing predominantly serous acini that produce a watery saliva rich in salivary amylase.

Serous Demilunes

Crescent-shaped caps of serous secretory cells that surround mucous acini in mixed salivary glands (such as the submandibular gland).

Portal Triad

A distinctive triad of vessels positioned at the corners of hepatic lobules, consisting of a branch of the hepatic artery, a branch of the hepatic portal vein, and a bile duct.

Kupffer Cells

Specialized resident macrophages lining hepatic sinusoids that phagocytose worn-out erythrocytes, bacteria, and particulate debris from the bloodstream.

Ito (Stellate) Cells

Perisinusoidal hepatic cells located within the space of Disse that store vitamin A and fat, possessing the capacity to differentiate into myofibroblasts and deposit collagen during liver injury.

Space of Disse

The perisinusoidal extracellular cleft separating sinusoidal endothelial cells from hepatocytes, facilitating the direct exchange of nutrients and metabolites via hepatocyte microvilli.