Anatomy and Physiology: Muscular, Digestive, and Endocrine Systems

Comprehensive vocabulary flashcards covering skeletal muscle physiology and anatomy, peripheral innervation, digestive tract structures and pathologies, and endocrine organs and hormone pathways.

Excitability

The ability of muscle tissue to receive and respond to stimuli, such as nerve signals.

Contractility

The ability of muscle tissue to shorten and generate force.

Extensibility

The ability of muscle tissue to stretch without being damaged.

Elasticity

The ability of muscle tissue to return to its original shape after being stretched or contracted.

Conductivity

The ability of muscle tissue to transmit electrical signals along the muscle cell membrane.

Epimysium

Connective tissue sheath that surrounds the entire muscle organ.

Perimysium

Connective tissue sheath that surrounds each fascicle.

Endomysium

Connective tissue sheath that surrounds each individual muscle fiber.

Deep fascia

Dense connective tissue that surrounds and separates muscles and muscle groups, helping to support and organize them.

Sarcolemma

The plasma membrane surrounding an individual skeletal muscle fiber.

Sarcoplasm

The cytoplasm of an individual muscle fiber.

Sarcoplasmic reticulum (SR)

Specialized smooth endoplasmic reticulum in muscle fibers that stores and releases calcium ions needed for muscle contraction.

T-tubules (transverse tubules)

Invaginations of the sarcolemma that carry electrical impulses deep into the interior of the muscle fiber.

Myoglobin

A protein in muscle cells that binds and stores oxygen.

Sarcomere

The basic functional contractile unit of skeletal muscle that extends from one Z disc to the next.

Z discs

Protein boundaries of a sarcomere that serve as the attachment points for thin filaments.

A band

The dark region of a sarcomere that spans the entire length of the thick filaments.

I band

The light region of a sarcomere that contains only thin (actin) filaments.

H zone

The central region of a relaxed sarcomere that contains only thick (myosin) filaments.

M line

A structural line in the exact middle of the sarcomere that holds thick filaments in place.

Tendon

Strong, cordlike connective tissue that attaches muscle to bone.

Aponeurosis

A broad, flat sheet of connective tissue that attaches muscles to other muscles or bones.

Sliding filament mechanism

The process of muscle contraction where thin actin filaments slide past thick myosin filaments without either filament shortening, causing the sarcomere to shorten.

Neuromuscular junction (NMJ)

The specialized synapse or connection between a motor neuron and a skeletal muscle fiber.

Motor end plate

Specialized region of the muscle fiber sarcolemma containing acetylcholine (ACh) receptors opposite the synaptic terminal.

Tetanus (condition)

A disorder caused by a toxin from Clostridium tetani bacteria entering via wounds, characterized by severe muscle spasms, stiffness, and lockjaw.

Botulism

A condition caused by botulinum toxin from Clostridium botulinum bacteria that prevents normal muscle contraction by blocking acetylcholine release.

Motor unit

A functional unit consisting of a single motor neuron and all the skeletal muscle fibers it innervates.

Rigor mortis

Postmortem muscle stiffness that occurs as ATP is depleted, preventing myosin heads from detaching from actin filaments.

Isometric contraction

A muscle contraction where tension is generated without a change in muscle length, such as holding a plank.

Concentric isotonic contraction

A dynamic contraction in which the muscle shortens while producing force, such as lifting a dumbbell.

Eccentric isotonic contraction

A dynamic contraction in which the muscle lengthens while producing force, such as slowly lowering a dumbbell.

Slow oxidative fibers

Red skeletal muscle fibers with high myoglobin, many mitochondria, and high fatigue resistance suited for endurance and posture.

Fast glycolytic fibers

White skeletal muscle fibers with low myoglobin, few mitochondria, and low fatigue resistance adapted for short, powerful bursts of movement.

Hypertrophy

An increase in overall muscle size resulting from the enlargement of preexisting muscle fibers.

Atrophy

A decrease in muscle size and mass due to inactivity, aging, disease, or lack of neural stimulation.

Agonist (prime mover)

The primary muscle directly responsible for producing a specific anatomical movement.

Antagonist

A muscle that opposes or reverses the action of a specific prime mover.

Synergist

A muscle that assists the prime mover in performing an action or helps stabilize an adjacent joint.

Sarcopenia

The age-related progressive loss of skeletal muscle mass and strength.

Duchenne muscular dystrophy

A severe inherited form of muscular dystrophy affecting primarily boys, caused by mutations in the dystrophin protein.

Myasthenia gravis

An autoimmune disorder where autoantibodies attack acetylcholine receptors at the neuromuscular junction, leading to progressive muscle weakness.

Trigeminal nerve (CN V)

Cranial nerve whose mandibular division (V3) provides motor innervation to the muscles of mastication.

Facial nerve (CN VII)

Cranial nerve responsible for motor control of the muscles of facial expression.

Phrenic nerve

Nerve that provides motor and sensory innervation to the diaphragm.

Bell palsy

Sudden unilateral facial weakness or paralysis caused by inflammation or dysfunction of the facial nerve (CN VII).

Lateral epicondylitis

Also called tennis elbow; an overuse injury affecting the common extensor tendons near the lateral epicondyle of the humerus.

Carpal tunnel syndrome

Neuropathy caused by compression of the median nerve within the carpal tunnel at the wrist.

Compartment syndrome

A medical emergency characterized by elevated pressure within an inelastic fascial muscle compartment, treated by surgical fasciotomy.

Bolus

A rounded mass of chewed food mixed with saliva prepared for swallowing.

Parotid gland

Salivary gland located anterior and inferior to each ear that produces watery saliva containing salivary amylase.

Submandibular gland

Salivary gland located beneath the mandible that secretes the majority of resting saliva.

Sublingual gland

Salivary gland positioned beneath the tongue that secretes mostly mucus-rich saliva.

Deciduous teeth

The primary dentition (baby teeth) consisting of $20$ teeth: $8$ incisors, $4$ canines, and $8$ molars (no premolars).

Permanent teeth

The adult dentition consisting of $32$ teeth: $8$ incisors, $4$ canines, $8$ premolars, and $12$ molars.

Nasopharynx

The superior region of the pharynx located posterior to the nasal cavity that functions solely in conducting air.

Oropharynx

The middle region of the pharynx located posterior to the oral cavity that serves as a common passageway for food, liquid, and air.

Laryngopharynx

The inferior portion of the pharynx that connects to both the larynx and esophagus, conducting food, liquid, and air.

Peritoneum

Serous membrane comprising a parietal layer lining the abdominal wall and a visceral layer covering abdominal viscera.

Mesentery

A double fold of visceral peritoneum that suspends GI organs and conveys neurovascular and lymphatic structures.

Mucosa

The innermost tunic of the alimentary canal consisting of an epithelium, lamina propria, and muscularis mucosae.

Muscularis

The GI wall tunic typically composed of inner circular and outer longitudinal smooth muscle layers containing the myenteric nerve plexus.

Adventitia

A dense fibrous connective tissue covering found on retroperitoneal organs in place of serosa.

Upper esophageal sphincter

Muscular ring at the superior end of the esophagus that relaxes during swallowing to admit the food bolus.

Lower esophageal (cardiac) sphincter

Muscular ring at the junction of the esophagus and stomach that prevents reflux of acidic gastric juice into the esophagus.

Buccal phase

The first and only voluntary phase of swallowing, during which the tongue pushes the bolus posteriorly toward the pharynx.

Gastroesophageal reflux disease (GERD)

Chronic condition marked by frequent backflow of gastric contents into the esophagus due to an incompetent lower esophageal sphincter.

Gastric folds (rugae)

Longitudinal mucosal folds inside the stomach that unfold to allow organ expansion upon filling.

Pyloric sphincter

Thick smooth muscle valve that regulates the passage of chyme from the pylorus of the stomach into the duodenum.

Chyme

The acidic, semifluid paste of partially digested food and gastric secretions produced by the stomach.

Duodenum

The initial $C$-shaped segment of the small intestine that receives chyme, bile, and pancreatic enzymes.

Jejunum

The middle division of the small intestine responsible for the majority of chemical digestion and nutrient absorption.

Ileum

The terminal portion of the small intestine that absorbs bile salts, vitamin B12, and remaining nutrients.

Major duodenal papilla

Anatomical opening in the duodenum through which bile and pancreatic juice enter via the hepatopancreatic ampulla.

Peyer's patches

Aggregated lymphoid nodules located within the submucosa of the small intestine that monitor and defend against enteric pathogens.

Vermiform appendix

A slender blind-ended pouch containing lymphoid tissue that projects from the posteromedial surface of the cecum.

Diverticulosis

The formation of small, abnormal herniations or pouches (diverticula) through weak areas of the colon wall.

Diverticulitis

Inflammation or infection involving one or more diverticula in the large intestine.

Falciform ligament

A peritoneal fold that divides the anatomical right and left lobes of the liver anteriorly and anchors it to the abdominal wall and diaphragm.

Round ligament of the liver (ligamentum teres)

The fibrous cord remnant of the obliterated fetal umbilical vein found on the inferior edge of the falciform ligament.

Cirrhosis

A chronic liver disease marked by diffuse fibrous scarring and nodular regeneration that replaces normal hepatic architecture.

Cystic duct

The duct through which bile enters and exits the gallbladder, connecting to the common hepatic duct.

Common bile duct

The biliary conduit formed by the union of the cystic duct and common hepatic duct that delivers bile to the duodenum.

Cholelithiasis

The presence of solid concretions (gallstones) within the gallbladder or biliary tract, usually formed from cholesterol or bilirubin.

Celiac disease

An autoimmune reaction triggered by dietary gluten that damages small intestinal mucosa and blunts intestinal villi.

Hypothalamo-hypophyseal portal system

A specialized vascular bed of capillaries and venules delivering releasing and inhibiting hormones from the hypothalamus to the anterior pituitary.

Hypothalamo-hypophyseal tract

Unmyelinated neurosecretory axons running from hypothalamic nuclei through the infundibulum to transport oxytocin and ADH to the posterior pituitary.

Anterior pituitary (adenohypophysis)

The glandular lobe of the pituitary gland that synthesizes and secretes its own hormones in response to hypothalamic releasing and inhibiting factors.

Posterior pituitary (neurohypophysis)

The neural lobe of the pituitary gland that stores and releases antidiuretic hormone (ADH) and oxytocin produced by hypothalamic neurons.

Calcitonin

A thyroid hormone secreted by parafollicular cells that lowers blood calcium levels by inhibiting osteoclast activity and bone breakdown.

Parathyroid hormone (PTH)

Hormone secreted by parathyroid glands that increases blood calcium by stimulating osteoclasts, renal calcium reabsorption, and vitamin D activation.

Adrenal cortex

The outer glandular region of the adrenal gland that secretes steroid hormones including aldosterone, cortisol, and androgens.

Adrenal medulla

The inner modified sympathetic neuroendocrine core of the adrenal gland that secretes the catecholamines epinephrine and norepinephrine.

Aldosterone

A mineralocorticoid produced by the adrenal cortex that regulates sodium retention, potassium excretion, and blood pressure.

Cortisol

A glucocorticoid secreted by the adrenal cortex that modulates carbohydrate metabolism and mediates the physiological stress response.

Insulin

An endocrine hormone produced by pancreatic beta cells that decreases blood glucose by stimulating cellular glucose uptake and glycogen synthesis.

Glucagon

An endocrine hormone produced by pancreatic alpha cells that elevates blood glucose by stimulating glycogen breakdown in the liver.

Pineal gland

A small neuroendocrine gland located near the roof of the third ventricle of the brain that secretes melatonin to regulate sleep-wake cycles.

Thymus

A bilobed cervicothoracic organ behind the sternum that produces thymic hormones essential for the differentiation and maturation of T lymphocytes.