Anatomy Unit 2 Test

Amnion / Amniotic Cavity

A fluid-filled sac that surrounds and cushions the developing embryo.  

Blastocoel

The fluid-filled internal cavity of a blastocyst.  

Blastocyst

A stage of early development featuring an inner cell mass, outer trophoblast, and fluid cavity.  

Blastopore

An indentation formed during gastrulation as surface cells move inward.  

Cervix

The lower, narrow entrance of the uterus connecting to the vagina.  

Cleavage

Rapid cell division of the zygote following fertilization without overall growth in size.  

Ectoderm

The outermost primary germ layer that gives rise to the skin, hair, nails, and nervous system.  

Endoderm

The innermost primary germ layer forming the lining of the digestive tract, liver, pancreas, and lungs.  

Endometrium

The inner mucosal lining of the uterus where the blastocyst implants.

Gastrulation

The developmental process where a single-layered structure reorganizes into three primary germ layers.  

Human Chorionic Gonadotropin (hCG)

A hormone secreted by the early blastocyst/trophoblast that maintains pregnancy hormone levels.  

Implantation

The process wherein the blastocyst embeds into the endometrial lining of the uterus.  

Inner Cell Mass (ICM) / Embryoblast

The internal cluster of cells in a blastocyst that develops into the actual embryo.  

Mesoderm

The middle primary germ layer giving rise to muscles, bones, the circulatory system, and kidneys.  

Morula

A solid ball of 10 to 30 cells resulting from early cleavage divisions.  

Neural Tube

An embryonic precursor structure to the central nervous system (brain and spinal cord).  

Notochord

A midline rod-like structure that defines the embryo's axis and induces neural tube formation.  

Organogenesis

The stage of embryonic development during which organ systems begin to form.  

Ovary

The female reproductive organ that produces eggs and hormones such as estrogen and progesterone.  

Ovulation

The release of a mature egg from the ovary into the fallopian tube.  

Pharyngeal Arches

Embryonic structures that give rise to facial features, jaw elements, and neck tissues.  

Placenta

The organ connecting the embryo/fetus to the uterine wall for gas exchange, nutrient delivery, and waste removal.  

Primitive Streak

A structural groove formed on the epiblast during early gastrulation that establishes bilateral symmetry.  

Somites

Paired blocks of mesoderm alongside the neural tube that develop into skeletal muscle, vertebrae, and skin.

Syncytiotrophoblast

The outer invasive layer of the trophoblast that secretes enzymes (gelatinase) to break down endometrial tissue.  

Trophoblast

The outer cell layer of the blastocyst that aids in implantation and placenta creation.  

Umbilical Cord

The vascular conduit connecting the developing fetus to the placenta.  

Uterine (Fallopian) Tube

The canal through which the egg travels from the ovary to the uterus. 

Yolk Sac

An extraembryonic structure providing early nutrients and early site of blood cell formation.  

Zona Pellucida

The protective membrane surrounding the oocyte and early-stage embryo. 

Zygote

The single-celled fertilized egg resulting from the union of a sperm cell and an egg cell.  

Amniotic sac

A fluid-filled protective bubble formed as the embryonic germ layers fold and pinch off.  

Anaphase

The stage of mitosis where sister chromatids are pulled apart to opposite sides of the cell. 

Blastocyst (or Blastula)

A hollow sphere of about 120 cells consisting of an inner cell mass and an outer trophoblast layer.  

Cell cycle

The regulated sequence of cell growth, interphase, and mitotic division.

Cytokinesis

The division of the cell cytoplasm resulting in two distinct daughter cells.  

Differentiation

The process by which unspecialized stem cells become specialized cell types and tissues.  

Ectoderm

The outer germ layer of an embryo that forms the nervous system, brain, and epidermal epithelium. 

Embryo

The developmental stage of a human from week 3 through week 8 following fertilization.  

Embryology

The biological study of embryo development.  

Endoderm

The interior germ layer of an embryo that develops into the epithelium of internal organs and the respiratory system.  

Fertilization

The fusion of male (sperm) and female (oocyte) pronuclei to form a complete zygote.  

Fetal development

The stage of human development from 9 weeks through birth, during which major organ systems mature.  

Gastrula

An embryo stage following the blastocyst that is organized into three primary germ layers.  

Germinal development

The first two weeks of embryonic development following fertilization.  

Hematopoietic stem cells

Multipotent stem cells in the bone marrow that produce all blood cell types.  

Induced pluripotent stem cells (iPSCs)

Adult unipotent stem cells that are reprogrammed in a laboratory setting to behave like embryonic pluripotent cells.  

Inner cell mass

A cluster of pluripotent cells located inside the blastocyst that gives rise to the body of the embryo.  

Interphase

The non-dividing phase of the cell cycle (G1G1, S, G2G2) where a cell grows, performs functions, and replicates DNA.  

Mesoderm

The middle germ layer of an embryo that forms muscle tissue, bones, and connective tissues.  

Metaphase

The phase of mitosis where chromosomes align along the middle of the cell.  

Mitosis

The process of cellular division used for growth, development, and tissue repair.  

Morula

A solid ball of approximately 16 to 32 cells created through early cleavage divisions.  

Multipotent stem cells

Stem cells capable of differentiating into multiple cell types within a specific organ system or tissue type.  

Oocyte (Ovum)

The female egg cell.  

Pluripotent stem cells

Stem cells that can differentiate into almost any cell type across specific tissue lineages.  

Prophase

The initial phase of mitosis where the nuclear membrane disappears and chromatin condenses.  

Stem cells

Designated cells capable of self-renewal and division to maintain or replace damaged body tissues.  

Telophase

The final phase of mitosis where two nuclear membranes reform, yielding two identical nuclei.  

Totipotent stem cells

Stem cells with the capability to differentiate into any cell type required to form a complete organism.  

Trophoblast

The outer cell layer of a blastocyst that facilitates implantation into the uterine wall and placenta development.  

Unipotent stem cells

Stem cells that can only differentiate into a single, specialized cell type. 

Zona pellucida

The protective outer membrane of an oocyte that sperm must penetrate for fertilization.  

Zygote

The initial single cell formed immediately upon the fusion of egg and sperm nuclei.  

Adipocyte

A fat cell that stores energy as fat and provides insulation and cushioning.

Adipose tissue

Fatty body tissue composed of adipocytes that acts as an energy reserve, insulates the body, and protects organs.

Angiogenesis

The biological process of growing new blood vessels from existing ones.

Apical surface

The exposed, outer, or top edge of an epithelial cell or tissue layer facing a cavity, organ lumen, or the outside environment.

Apoptosis

Programmed, controlled cell death used by the body to remove old, damaged, or unneeded cells.

Areolar (loose) connective tissue

A flexible, gel-like tissue that cushions organs, holds skin in place, and acts as a soft wrapping material around tissues.

Axon

The long, tail-like tail extension of a neuron that carries electrical impulses away from the cell body toward other cells.

Basement membrane

A thin, sticky structural layer that anchors epithelial tissue to the underlying connective tissue.

Benign

Non-cancerous; refers to a growth or tumor that does not spread to other tissues or parts of the body.

Biopsy

The surgical removal of a small sample of tissue from the body to examine it for disease or abnormal cells.

Blood

A liquid connective tissue composed of cells (red cells, white cells, platelets) suspended in a watery fluid called plasma.

Blood vessels

Tube-like structures (arteries, veins, capillaries) that transport blood throughout the entire body.

Bone

A hard, dense connective tissue composed of cells embedded in a rigid matrix of calcium salts and collagen fibers, providing structural support and protection.

Carcinogen

Any substance, agent, or radiation capable of causing cancer by damaging DNA.

Carcinoma

A type of cancer that originates in epithelial tissues (the outer skin or lining of internal organs).

Cardiac muscle

Involuntary, striated muscle tissue found exclusively in the walls of the heart that pumps blood.

Cell body (soma)

The core part of a neuron containing the nucleus and most organelles, which integrates incoming signals.

Cell membrane

The flexible, semi-permeable outer boundary of a cell that regulates what enters and exits the cell.

Cell organelles (structure/function)

Specialized internal structures within a cell that perform specific metabolic tasks (e.g., mitochondria for power, ribosomes for protein synthesis).

Cilia

Tiny, hair-like projections on the surface of certain cells that beat rhythmically to move fluids or particles across the cell surface.

Compact bone

Dense, solid, and hard outer layer of bone tissue that provides strength and structural support.

Connective tissue

One of the four main tissue types; it connects, supports, binds, cushions, or protects other body tissues and organs.

Collagen fibers

Strong, flexible, rope-like protein fibers that give connective tissues high tensile strength to resist stretching.

Columnar

Tall, column-shaped epithelial cells that are taller than they are wide.

Cytoskeleton

An internal network of microfilaments and microtubules that gives a cell its shape, internal organization, and movement capability.

Dendrites

Short, branch-like extensions of a neuron that receive electrical signals from other cells and carry them toward the cell body.

Dense regular connective tissue

Strong tissue packed tightly with parallel collagen fibers, designed to resist force in one direction (found in tendons and ligaments).

Dermis

The thick, tough inner layer of skin beneath the epidermis, rich in connective tissue, blood vessels, and nerves.

Desmosomes

Strong, spot-weld junction structures that physically anchor adjacent cells together to resist tearing.

Diffusion

The passive movement of molecules or particles from an area of higher concentration to an area of lower concentration.

Elastic fibers

Flexible protein fibers made of elastin that allow tissues to stretch and spring back into their original shape.

Elastic tissue

A flexible connective tissue rich in elastic fibers, allowing structures like arteries and lungs to expand and recoil.

Endocrine glands

Ductless glands that secrete chemical signals (hormones) directly into the bloodstream or tissue fluid.

Epithelium / epithelial tissue

Sheets of tightly packed cells that line body surfaces, internal cavities, and organs, acting as protective barriers and absorption sites.

Exocrine glands

Glands that secrete their products through ducts onto a body surface or into an internal cavity (e.g., sweat, saliva, digestive juice glands).

Extracellular matrix

The non-living material surrounding cells in a tissue, consisting of ground substance (fluid/gel) and structural protein fibers.