Integrated Veterinary Anatomy, Physiology, and Development

Comprehensive vocabulary flashcards covering animal musculoskeletal mechanics, bone histology, embryology, developmental signaling, neuroanatomy, autonomic outflow, membrane transport, and cardiac physiology.

Pennate muscle

A feather-like muscle arrangement where fibres attach at an angle between internal and external aponeuroses, packing more sarcomeres into the tissue to increase Physiological Cross Sectional Area (PCSA) and power.

Physiological Cross Sectional Area (PCSA)

A physiological measurement of the total cross-sectional area of all muscle fibres perpendicular to their orientation, which is directly proportional to maximum muscle force.

Parallel muscle

A muscle architecture where fibres run parallel to the line of action, featuring long fibres suited for extensive shortening distance, wide range of motion, and performing mechanical work.

Lacertus fibrosus

A long tendon in the horse extending from the shoulder to the phalanges that stores elastic potential energy during late stance and rapidly recoils to swing the limb forward.

Diaphysis

The narrow, tubular, load-bearing central shaft of a long bone.

Epiphysis

The expanded terminal end of a long bone that articulates with an adjacent bone and is capped by articular cartilage.

Metaphysis

The neck region of a long bone positioned between the diaphysis and epiphysis where the epiphyseal growth plate resides.

Periosteum

A two-layered vascularized and innervated connective tissue membrane enclosing the outer surface of bone, containing osteogenic cells and osteoblasts for external bone deposition.

Endosteum

A thin single-cell layer lining the internal medullary cavity of bone where osteoblasts and osteoclasts reside to carry out bone remodeling and resorption.

Osteon

The basic microscopic structural unit of compact cortical bone, consisting of concentric lamellae and lacunae enclosing osteocytes arranged around a central neurovascular canal.

Osteoblast

A mononucleated bone-forming cell residing on bone surfaces that synthesizes, secretes, and deposits unmineralized organic bone matrix (osteoid).

Osteoclast

A specialized cell found on inner bone surfaces that secretes acid and proteolytic enzymes to break down, demineralize, and resorb old or unwanted bone matrix.

Osteocyte

A mature bone cell trapped within a lacuna inside the mineralized matrix that maintains bone tissue integrity and participates in cellular communication networks.

Sesamoid bone

A specialized bone (such as the patella) embedded within a tendon that increases mechanical leverage across a joint and redirects muscular force.

Articular cartilage

A smooth, avascular, and aneural layer of hyaline cartilage covering the epiphysis within synovial joints to minimize friction and absorb shock.

Synovial fluid

A viscous, hyaluronic acid-rich fluid secreted by the synovial membrane that lubricates articular surfaces, absorbs mechanical impact, and supplies nutrients to chondrocytes.

Meniscus

A crescent-shaped fibrocartilaginous disc located within a synovial joint cavity that enhances structural congruency and prevents abnormal joint movement.

Bursa

A closed, fluid-filled synovial sac positioned near joints where tendons glide across bony prominences to alleviate friction.

Synsarcosis

A muscular joint attachment between a limb and the trunk lacking a true bony articulation, such as the attachment of the mammalian scapula to the thorax.

Extracellular matrix (ECM)

A non-cellular network of fibrous macromolecules (collagen, elastin) and hydrated ground substance (proteoglycans) that provides structural scaffolding and biochemical cues to cells.

Glycosaminoglycans (GAGs)

Unbranched, repeating polysaccharide chains (e.g., hyaluronic acid, chondroitin sulphate) that carry negative charges to trap water and resist compressive forces.

Proteoglycan

A high-molecular-weight macromolecule consisting of a central core protein covalently linked to repeating glycosaminoglycan chains that provides space-filling scaffolding and compressive resistance in tissues.

Wolff's Law

The anatomical principle establishing that mechanical stress imposed on living bone regulates its growth and architecture, causing trabeculae to align along directions of functional load.

Intramembranous ossification

The direct embryological formation of bone tissue from clustered mesenchymal stem cells that differentiate into osteoblasts without a cartilaginous precursor.

Endochondral ossification

The developmental process by which a preexisting hyaline cartilage model is progressively degraded, vascularized, and replaced by mineralized bone tissue.

Blastomere

An individual, undifferentiated cell produced by early mitotic cleavage divisions of the fertilized zygote within the confining zona pellucida.

Morula

A solid, mulberry-like ball of blastomeres formed at the $16$-cell stage that undergoes compaction to segregate into an inner cell core and a peripheral outer layer.

Trophoblast

The outer epithelial cell layer of the blastocyst that pumps fluid into the central cavity, facilitates uterine implantation, and contributes to the fetal placenta.

Inner cell mass (ICM)

The pluripotent cell population clustered at one interior pole of the blastocyst that gives rise to the embryo proper.

Syncytiotrophoblast

A multinucleated, invasive syncytial mass formed by fused trophoblast cells that erodes into the maternal endometrium and secretes hCG to maintain pregnancy.

Epiblast

The dorsal columnar cell layer of the bilaminar embryonic disc that gives rise to all three primary germ layers during gastrulation.

Hypoblast

The ventral cuboidal cell layer of the bilaminar embryonic disc facing the blastocyst cavity that contributes to the yolk sac lining and extraembryonic membranes.

Gastrulation

The dynamic morphogenetic process by which cells from the epiblast ingress to transform a bilaminar embryonic disc into a trilaminar embryo of ectoderm, mesoderm, and endoderm.

Primitive streak

A linear transient structure formed along the posterior midline of the epiblast through which prospective endodermal and mesodermal cells migrate internally.

Somite

A paired block of paraxial mesoderm that segments periodically along both flanks of the neural tube to generate axial skeletal, muscular, and dermal tissues.

Sclerotome

The ventromedial mesenchymal compartment of a somite induced by Sonic hedgehog that undergoes resegmentation and surrounds the neural tube to form vertebrae and ribs.

Apical Ectodermal Ridge (AER)

A specialized pseudostratified ectodermal ridge capping the distal border of the limb bud that stimulates underlying mesenchymal proliferation and drives proximodistal outgrowth.

Zone of Polarizing Activity (ZPA)

A signaling region situated at the posterior margin of the developing limb bud that secretes Sonic hedgehog ($\text{Shh}$) to pattern the antero-posterior digit axis.

Mitotic spindle

A bipolar microtubule array assembled by centrosomes during mitosis that attaches to chromosomal kinetochores to pull sister chromatids apart.

Saltatory conduction

The rapid jumping propagation of an electrical action potential from one node of Ranvier to another along a myelinated axon.

Vomeronasal organ

An auxiliary olfactory structure located at the base of the nasal cavity that communicates with the oral cavity to detect volatile pheromones involved in reproductive and social behavior.

Enteric Nervous System

An intrinsic, largely autonomous division of the autonomic nervous system embedded within the walls of the gastrointestinal tract that coordinates local motility and secretion.

Craniosacral outflow

The anatomical organization of the parasympathetic nervous system originating from cranial nerves $\text{III}$, $\text{VII}$, $\text{IX}$, and $\text{X}$ and sacral spinal cord segments $\text{S1}$ to $\text{S3}$.

Thoracolumbar outflow

The anatomical organization of the sympathetic nervous system issuing from thoracic and upper lumbar spinal cord segments $\text{T1}$ to $\text{L4}$.

Vagosympathetic trunk

A paired composite nerve trunk enclosed in the carotid sheath containing caudally descending parasympathetic vagal fibres and cranially ascending sympathetic fibres.

G-protein coupled receptors (GPCRs)

A large superfamily of $7$-pass transmembrane cell surface receptors that transduce extracellular stimuli to trimeric G-proteins, regulating intracellular secondary messengers such as $\text{cAMP}$, $\text{IP}_3$, and $\text{DAG}$.

Elastic vessels

Large conducting arteries with highly compliant, elastic walls that store stroke volume during systole and convert intermittent ventricular ejection into continuous downstream flow.

Capacitance vessels

Thin-walled, highly distensible venules and systemic veins that serve as low-pressure volume reservoirs and govern cardiac filling pressure.

Sinoatrial (SA) node

The primary intrinsic pacemaker tissue situated in the right atrial wall that spontaneously depolarizes to initiate rhythmic cardiac contractions at approximately $75\,\text{bpm}$ at rest.

Purkinje fibres

Specialized, non-contractile modified cardiac myocytes of the ventricular conduction system that rapidly propagate electrical depolarization through ventricular muscle walls.