Cells and Tissues: Human Anatomy and Physiology

Comprehensive vocabulary flashcard set covering cellular structures, organelles, membrane transport, cell life cycle, protein synthesis, body tissue types, and wound repair based on lecture notes.

Cell

The smallest unit, or the building block, of all living things; first named in the late 1600s by Robert Hooke after the small cubelike rooms in a monastery.

Electrolytes

Metals in their ionic form (such as calcium, sodium, and potassium) that can carry an electrical charge and are essential for nerve impulse transmission and muscle contraction.

Interstitial Fluid

A dilute saltwater solution derived from blood that continuously bathes the exterior of all body cells and facilitates all nutrient and waste exchanges between cells and blood.

Generalized Cell

A conceptual cell demonstrating typical structures and functions common to all cells, organized into three main regions: the nucleus, cytoplasm, and plasma membrane.

Nucleus

The gene-containing control center or headquarters of a cell that houses genetic material ($\text{DNA}$) containing instructions for building proteins and cell reproduction.

Nuclear Envelope

A double membrane barrier enclosing the cell nucleus penetrated by relatively large nuclear pores and enclosing a jellylike fluid called nucleoplasm.

Nucleoli

Small, dark-staining round bodies located within the nucleus that serve as the assembly sites for ribosomes.

Chromatin

A loose network of bumpy threads scattered throughout the nucleus when a cell is not dividing, formed by $\text{DNA}$ combined with protein.

Chromosomes

Dense, rodlike bodies formed when chromatin threads coil and condense during cell division to facilitate the distribution of genetic material.

Plasma Membrane

A fragile, transparent, flexible outer limiting barrier composed of a phospholipid bilayer with floating proteins and cholesterol that encloses cell contents.

Phospholipids

Lipid molecules forming the membrane bilayer with hydrophilic ("water loving") polar heads on the outer surfaces and hydrophobic ("water hating") nonpolar tails in the center.

Glycocalyx

A sticky, sugar-rich, fuzzy area on the cell exterior composed of branching sugar-protein complexes (glycoproteins) that determines blood type and mediates cell-to-cell interactions.

Microvilli

Tiny, fingerlike projections of the plasma membrane that greatly increase cell surface area for absorption, commonly seen in epithelial cells of the small intestine.

Tight Junctions

Impermeable junctions formed by adjacent plasma membranes fusing together like a zipper, binding cells into leakproof sheets that prevent substances from passing through intercellular space.

Desmosomes

Anchoring junctions consisting of buttonlike membrane thickenings (plaques) connected by protein filaments that act as internal guy wires to prevent cells from pulling apart under mechanical stress.

Gap Junctions

Communicating junctions consisting of hollow protein cylinders called connexons that span adjacent membranes, allowing nutrients, ions, and chemical signals to pass directly between cells.

Cytoplasm

The cellular factory area outside the nucleus and inside the plasma membrane containing three major elements: cytosol, organelles, and inclusions.

Cytosol

The semitransparent fluid portion of the cytoplasm, composed largely of water, in which organelles, inclusions, nutrients, and other solutes are suspended.

Inclusions

Chemical substances present in specific cell types serving mostly as stored nutrients or cell products, including lipid droplets, glycogen granules, pigments like melanin, and crystals.

Mitochondria

Double-membraned "powerhouses" of the cell with an inner membrane folded into cristae; they break down foods using oxygen to produce $\text{ATP}$.

Ribosomes

Tiny, bilobed dark bodies made of proteins and ribosomal $\text{RNA}$ ($\text{rRNA}$) that serve as the actual sites of protein synthesis in the cell.

Rough Endoplasmic Reticulum

A membranous network of fluid-filled cisterns studded with ribosomes that serves as the cell's membrane factory and folds newly synthesized proteins into transport vesicles.

Smooth Endoplasmic Reticulum

A tubular organelle lacking ribosomes that functions in lipid metabolism (cholesterol and fat synthesis/breakdown) and the detoxification of drugs and pesticides.

Golgi Apparatus

A stack of flattened membranous sacs close to the nucleus that functions as the principal traffic director to modify, sort, and package proteins into secretory vesicles, membrane components, or lysosomes.

Lysosomes

Membranous bags packed with hydrolytic enzymes manufactured by ribosomes and packaged by the Golgi apparatus that digest worn-out cell structures and foreign material.

Peroxisomes

Membranous sacs of oxidase enzymes that detoxify harmful substances and neutralize free radicals into hydrogen peroxide ($\text{H}_2\text{O}_2$), which catalase converts to water ($\text{H}_2\text{O}$).

Cytoskeleton

An elaborate internal network of protein structures—microtubules ($25\,\text{nm}$), intermediate filaments ($10\,\text{nm}$), and microfilaments ($7\,\text{nm}$)—furnishing cellular framework and motility.

Centrioles

Paired, rod-shaped bodies composed of fine microtubules that lie at right angles near the nucleus, directing mitotic spindle assembly and cilia/flagella formation.

Cilia

Whiplike cellular extensions that sprout from centrioles to move substances across the exposed surface of a cell, such as mucus in the respiratory tract.

Flagella

Substantially longer projections formed by centrioles that propel the cell itself; the only example in the human body is the sperm tail.

Selective Permeability

The property of a healthy barrier, such as the plasma membrane, that allows certain substances to pass through while excluding others.

Diffusion

The passive movement of molecules and ions down their concentration gradient from an area of higher concentration to an area of lower concentration driven by kinetic energy.

Simple Diffusion

The unassisted passive movement of lipid-soluble solutes or solutes small enough to pass through membrane pores directly across the plasma membrane.

Osmosis

The diffusion of water down its concentration gradient across a selectively permeable membrane via specific protein channels called aquaporins or the lipid bilayer.

Facilitated Diffusion

Passive transport providing passage for lipid-insoluble or large solutes (such as glucose) using protein membrane channels or carrier proteins down a concentration gradient.

Filtration

A passive process in which water and solutes are forced across a membrane or capillary wall by a hydrostatic pressure gradient from higher pressure to lower pressure.

Active Transport

Energy-requiring ($\text{ATP}$) transport process, or solute pumping, in which protein carriers move substances against concentration or electrical gradients.

Sodium-Potassium Pump

A solute pump that uses $\text{ATP}$ to transport three sodium ions ($3\,\text{Na}^+$) out of the cell and two potassium ions ($2\,\text{K}^+$) into the cell against their concentration gradients.

Hypertonic Solution

A solution containing a higher solute concentration than the cell interior, causing water to leave the cell and the cell to shrink or crenate.

Hypotonic Solution

A solution containing a lower solute concentration (and more water) than the cell interior, causing water to rush into the cell until it swells and bursts (lyses).

Exocytosis

A type of vesicular transport where membranous vesicles package substances, migrate to the plasma membrane, fuse, and rupture to eject contents out of the cell.

Endocytosis

An $\text{ATP}$-requiring vesicular process in which the cell engulfs extracellular materials by enclosing them within a membranous sac that detaches into the cytoplasm.

Phagocytosis

A protective form of endocytosis ("cell eating") where cells use cytoplasmic extensions (pseudopods) to engulf large particles, such as bacteria or dead debris.

Pinocytosis

A routine form of endocytosis ("cell drinking") in which the plasma membrane invaginates into a tiny pit to engulf droplets of extracellular fluid containing dissolved fats or proteins.

Receptor-Mediated Endocytosis

A highly selective cellular uptake mechanism where target molecules bind specifically to external membrane receptor proteins before being internalized in a vesicle.

Interphase

The metabolic phase and longest period of the cell cycle during which the cell grows, carries on normal activities, and replicates its $\text{DNA}$.

Mitosis

The process of nuclear division consisting of prophase, metaphase, anaphase, and telophase that produces two daughter nuclei identical to the parent nucleus.

Cytokinesis

The division of the cytoplasm that begins in late anaphase and telophase when a microfilament contractile ring forms a cleavage furrow to pinch the cell into two daughter cells.

Prophase

The first stage of mitosis in which chromatin coils into visible chromosomes (sister chromatids joined at a centromere), centrioles move apart, mitotic spindle forms, and the nuclear envelope disappears.

Metaphase

The stage of mitosis where chromosomes cluster and align along the metaphase plate in the center of the mitotic spindle midway between the centrioles.

Anaphase

The mitotic stage during which centromeres split and sister chromatids (now chromosomes) are drawn apart toward opposite poles of the cell.

Telophase

The stage of mitosis in which chromosomes at opposite poles uncoil back into chromatin, spindles break down, and nuclear envelopes and nucleoli reform.

Gene

A segment of $\text{DNA}$ that carries the instructional sequence of base triplets needed to build one protein or polypeptide chain.

Triplet

A sequence of three consecutive bases on a $\text{DNA}$ strand that codes for a specific amino acid.

Codon

A three-base complementary sequence on messenger $\text{RNA}$ ($\text{mRNA}$) transcribed from a corresponding $\text{DNA}$ triplet.

Anticodon

A specialized three-base sequence on the head of a transfer $\text{RNA}$ ($\text{tRNA}$) molecule that binds complementarily to a specific $\text{mRNA}$ codon.

Transcription

The phase of protein synthesis where the genetic base sequence of a $\text{DNA}$ gene is transferred into the complementary base sequence of $\text{mRNA}$.

Translation

The cytoplasmic phase of protein synthesis where $\text{mRNA}$ sequences are decoded at ribosomes by $\text{tRNA}$ molecules to assemble amino acids into a polypeptide.

Tissue

A group of cells that are similar in structure and function, classified into four primary body types: epithelium, connective tissue, nervous tissue, and muscle.

Epithelial Tissue

The avascular lining, covering, and glandular tissue of the body that rests on a basement membrane and exhibits an apical surface.

Basement Membrane

A structureless material secreted by epithelial cells and abutting connective tissue cells that supports the basal surface of epithelial tissue.

Simple Squamous Epithelium

A single layer of thin, flat cells fitted like floor tiles that forms serous membranes and facilitates rapid diffusion in capillary walls and lung air sacs.

Simple Columnar Epithelium

A single layer of tall, closely fitting cells containing mucus-secreting goblet cells that lines the digestive tract from stomach to anus.

Pseudostratified Columnar Epithelium

An epithelial layer where all cells rest on the basement membrane but vary in height, giving a false stratified appearance; its ciliated variety lines the respiratory tract.

Stratified Squamous Epithelium

The most common stratified epithelium in the body, consisting of multiple layers with squamous surface cells, found in areas receiving friction such as the skin, mouth, and esophagus.

Transitional Epithelium

A highly modified stratified epithelium lining the urinary bladder, ureters, and urethra, capable of sliding and flattening its domelike superficial cells when stretched by urine.

Endocrine Glands

Ductless glands that produce hormones and discharge them directly into the blood vessels that weave through them (e.g., thyroid, adrenals, pituitary).

Exocrine Glands

Glands that retain their ducts and empty secretions directly onto epithelial surfaces (e.g., sweat glands, oil glands, liver, and pancreas).

Extracellular Matrix

Nonliving substance produced and secreted outside connective tissue cells consisting of a structureless ground substance and embedded protein fibers.

Bone (Osseous Tissue)

Rigid connective tissue composed of osteocytes residing within lacunae, surrounded by layers of hard matrix containing calcium salts and collagen fibers.

Hyaline Cartilage

The most widespread cartilage, possessing abundant collagen fibers concealed by a rubbery, blue-white glassy matrix; found in the larynx, joints, ribs, and fetal skeleton.

Fibrocartilage

A highly compressible type of cartilage that forms cushionlike disks between the vertebrae of the spinal column.

Dense Connective Tissue

Connective tissue packed with collagen fibers produced by fibroblasts that forms strong, ropelike tendons (muscle to bone) and ligaments (bone to bone).

Areolar Tissue

Soft, pliable, cobwebby loose connective tissue acting as universal packing glue to hold internal organs together and forming the lamina propria beneath mucous membranes.

Edema

An abnormal swelling condition that occurs when inflamed areolar tissue absorbs excess fluid like a sponge.

Adipose Tissue

Fat tissue dominated by signet ring cells containing large lipid droplets that insulate, protect organs, and store fuel beneath the skin and around the kidneys.

Reticular Connective Tissue

A delicate network of interwoven reticular fibers and reticular cells that forms the internal stroma supporting free blood cells in lymphoid organs (spleen, lymph nodes, bone marrow).

Blood (Vascular Tissue)

An atypical connective tissue composed of blood cells surrounded by a nonliving fluid matrix called blood plasma with soluble clotting protein fibers.

Skeletal Muscle

Voluntary, striated muscle tissue composed of long, cylindrical, multinucleate cells that pull on bones or skin to generate gross body movements.

Cardiac Muscle

Involuntary, striated muscle tissue found only in the heart, consisting of uninucleate, branching cells connected by intercalated disks containing gap junctions.

Smooth Muscle

Visceral, involuntary, nonstriated muscle tissue composed of single-nucleus, spindle-shaped cells found in hollow organs that produces wavelike contractions (peristalsis).

Neurons

Specialized nervous system cells with long cytoplasmic processes that exhibit irritability and conductivity to receive and transmit electrochemical impulses.

Regeneration

A wound healing process in which destroyed tissue is replaced by the same kind of cells.

Fibrosis

A tissue repair mechanism involving dense fibrous connective tissue that results in the formation of non-functional scar tissue.

Granulation Tissue

A delicate, pink, fragile tissue composed of new budding capillaries, phagocytes, and fibroblasts that bridges tissue gaps during wound repair beneath a scab.

Amitotic Tissues

Tissues that almost completely lose their ability to divide upon full maturity (notably cardiac muscle and nervous tissue in the brain and spinal cord), which are permanently replaced by scar tissue when damaged.