{Pacinian corpuscle}{}{Named for Filippo Pacini, Italian anatomist, 1812-1883; oval receptor found in the deep dermis or hypodermis [responsible for deep cutaneous pressure and vibration] and in tendons (responsible for proprioception).}

{pain receptor}{}{Sensory nerve ending associated with the feeling of pain.}

{pancreas}{}{Abdominal gland that secretes pancreatic juice into the intestine and insulin and glucagon from the pancreatic islets into the bloodstream.}

{pancreatic duct}{}{Duct from the exocrine cells of the pancreas.}

{papilla [papillae]}{}{A small nipplelike process. Projection of the dermis, containing blood vessels and nerves, into the epidermis. Projections on the surface of the tongue.}

{paranasal sinus}{}{Air-filled cavity in cranial bone; lined with mucous membrane and connected to nasal cavity.}

{parasagittal plane}{}{A plane that separates the body into unequal right and left halves.}

{parasympathetic division}{}{Subdivision of the autonomic nervous system; characterized by having the cell bodies of its preganglionic neurons located in the brainstem and the sacral region of the spinal cord [craniosacral division]; usually involved in activating vegetative functions such as digestion, defecation, and urination.}

{parasympathetic nerve}{}{Nerve of the portion of the autonomic nervous system that arises from the brain and the sacral region of the spinal cord.}

{parathyroid gland}{}{One of four glandular masses imbedded in the posterior surface of the thyroid gland; secretes parathyroid hormone.}

{parathyroid hormone [PTH]}{}{Peptide hormone produced by the parathyroid gland; increases bone breakdown and blood calcium levels.}

{pars distalis}{}{The distal-most portion of the anterior pituitary.}

{pars intermedia}{}{The portion of the anterior pituitary immediately adjacent to the posterior pituitary.}

{pars tuberalis}{}{The proximal-most portion of the anterior pituitary.}

{parturition}{}{Giving birth.}

{peptide bond}{}{Chemical bond between amino acids.}

{peptide hormone}{}{A hormone made out of a short peptide sequence.}

{perimysium}{}{Fibrous sheath enveloping a bundle of skeletal muscle fibers [muscle fascicle].}

{periosteum}{}{Thick, double-layered connective tissue sheath covering the entire surface of a bone except the articular surface, which is covered with cartilage.}

{peripheral nervous system [PNS]}{}{Major subdivision of the nervous system consisting of nerves and ganglia.}

{peristalsis}{}{Rhythmic waves of muscular contraction in walls of certain tubular organs.}

{peritubular capillary}{}{Capillary that surrounds renal tubule and functions in reabsorption and secretion during urine formation.}

{permeability}{}{The ability of a substance to pass through a membrane or other barrier.}

{peroxisome}{}{Membrane-bound body similar to a lysosome in appearance but often smaller and irregular in shape; contains enzymes that either decompose or synthesize hydrogen peroxide.}

{pH}{}{The negative logarithm of the hydrogen ion concentration used to indicate the acidity or alkalinity of a solution; values range from 0 to 14.}

{phagocytosis}{}{Process of ingestion by cells of solid substances, such as other cells, bacteria, bits of necrosed tissue, and foreign particles.}

{pharynx}{}{Portion of digestive tube between mouth and esophagus.}

{phospholipid}{}{Lipid with phosphorus, resulting in a molecule with a polar end and a nonpolar end; main component of the lipid bilayer.}

{photoreceptor}{}{A sensory receptor that is sensitive to light. Examples are rods and cones of the retina.}

{physiology}{}{Study of body functions.}

{pia mater}{}{Delicate membrane forming the inner covering of the brain and spinal cord.}

{pinocytosis}{}{Cell drinking; uptake of liquid by a cell.}

{pituitary gland}{}{Endocrine gland attached to the hypothalamus by the infundibulum. Also called the hypophysis.}

{placenta}{}{Structure that attaches the fetus to the uterine wall, providing for delivery of nutrients to and removal of wastes from the fetus.}

{plantar flexion}{}{Flexing the foot at the ankle toward the sole [bending the foot downward].}

{plasma membrane}{}{Cell membrane.}

{polar covalent bond}{}{Covalent bond in which atoms do not share their electrons equally.}

{polymer}{}{A large organic molecule made up of two or more subunits or monomers.}

{polypeptide}{}{A compound formed by the union of many amino acid molecules.}

{polysaccharide}{}{Carbohydrate containing a large number of monosaccharide molecules.}

{pons}{}{That portion of the brainstem between the medulla and midbrain.}

{postcentral gyrus}{}{A fold in the cerebrum that lies just posterior to the central sulcus.}

{posterior}{}{Toward the back; the opposite of anterior.}

{posterior pituitary}{}{Lobe of pituitary gland that secretes oxytocin and antidiuretic hormone [vasopressin].}

{postsynaptic cell}{}{Refers to a nerve, muscle, or gland cell that is in close association with a presynaptic terminal. The postsynaptic cell membrane has receptor molecules within it that bind to neurotransmitter molecules.}

{potential energy}{}{Energy in a chemical bond that is not being exerted or used to do work.}

{power stroke}{}{Movement of the head of a filament of myosin, which causes the attached actin myofilament to slide past it.}

{precentral gyrus}{}{A fold in the cerebrum that lies just anterior to the central sulcus.}

{presynaptic cell}{}{A neuron that has an axon terminal next to another neuron, a gland, or a muscle forming a synapse.}

{presynaptic terminal}{}{Enlarged axon terminal or terminal bouton.}

{prometaphase}{}{Stage of mitosis in which the spindle forms, and kinetochores of chromosomes attach to the spindle fibers.}

{pronation}{}{Rotation of the forearm so that the anterior surface is down [prone].}

{prophase}{}{First stage in cell division when chromatin strands condense to form chromosomes.}

{prostaglandin}{}{Class of physiologically active substances present in many tissues; among effects are those of vasodilation, stimulation, and contraction of uterine smooth muscle, and promotion of inflammation and pain.}

{prostate gland}{}{Gland surrounding male urethra below urinary bladder that adds its secretion to semen just prior to ejaculation.}

{protein}{}{Macromolecule consisting of long sequences of amino acids linked together by peptide bonds.}

{proton}{}{Positively charged particle in the nuclei of atoms.}

{protraction}{}{Movement forward or in the anterior direction.}

{proximal}{}{Closer to midline or origin; opposite of distal.}

{proximal convoluted tubule}{}{Tubule that receives renal glomerular filtrate.}

{pseudostratified epithelium}{}{Epithelium consisting of a single layer of cells but having the appearance of multiple layers.}

{pulmonary circulation}{}{System of blood vessels that carries blood between heart and lungs.}

{pyloric sphincter}{}{Muscular junction between stomach and small intestine.}

{pyramidal cell}{}{Large, pyramid-shaped neuron within the cerebral cortex.}