A&P 2 Lecture - Chapter 29 Human Development and Aging

Zygote – A fertilized egg cell formed by the union of sperm and egg; the first cell of a new individual

Cleavage – Rapid mitotic divisions of the zygote that increase cell number without increasing size

Blastomeres – Individual cells resulting from cleavage of the zygote

Morula – A solid ball of 16+ blastomeres formed around day 3–4 post

fertilization

Blastocyst – A hollow ball of cells with a fluid

filled cavity (blastocoel), an inner cell mass (embryoblast), and an outer layer (trophoblast)

Embryoblast – The inner cell mass of the blastocyst that develops into the embryo

Trophoblast – The outer cell layer of the blastocyst that contributes to the placenta

Blastocoel – The fluid

filled internal cavity of the blastocyst

Implantation – The process by which the blastocyst embeds into the endometrium around day 6–7 post

fertilization

Preembryonic stage – Developmental stage from fertilization to day 16, including cleavage, implantation, and germ layer formation

Embryonic stage – Stage from day 16 to week 8 when the three germ layers form and organogenesis begins

Fetal stage – Stage from week 9 to birth, characterized by growth and organ maturation

Gastrulation – The process by which the three primary germ layers (ectoderm, mesoderm, endoderm) are formed from the embryonic disc

Embryogenesis – The developmental process that includes formation of the embryonic disc and differentiation of germ layers

Primitive streak – A thickened midline of epiblast cells that initiates gastrulation

Primitive groove – A depression in the primitive streak through which migrating cells form germ layers

Ectoderm – The outer germ layer that forms the epidermis, nervous system, eyes, and hair

Mesoderm – The middle germ layer that forms muscles, bones, blood, kidneys, dermis, and reproductive organs

Endoderm – The inner germ layer that forms the lining of the digestive and respiratory tracts and associated glands

Organogenesis – The differentiation of the three germ layers into organs and organ systems

Neural tube – A dorsal hollow tube derived from ectoderm that develops into the brain and spinal cord (CNS)

Embryonic disc – A flattened structure derived from the embryoblast that forms the basis of the three germ layers

Capacitation – A process that sperm undergo after ejaculation, making the membrane fragile and preparing it to fertilize an egg

Acrosome reaction – The release of enzymes from the sperm head to penetrate the zona pellucida of the egg

Fast block – A rapid depolarization of the egg membrane due to sodium influx, preventing polyspermy

Slow block – A longer

lasting response involving cortical granules that alters the zona pellucida to prevent additional sperm entry

Pronucleus – The separate nuclear material of the sperm and egg before they fuse to form the zygote nucleus

Amnion – A transparent sac that encloses the embryo and is filled with amniotic fluid

Amniotic fluid – Fluid that cushions the fetus, maintains temperature, allows movement, and aids lung development

Yolk sac – Early extraembryonic membrane that provides nutrients and is the first site of blood cell formation

Allantois – A small outpouching that helps form the umbilical cord and urinary bladder

Chorion – The outermost extraembryonic membrane that contributes to the placenta

Coelom – A body cavity located between the ectoderm and endoderm that develops into thoracic and abdominal cavities

Fertile window – The period from a few days before ovulation to 14–24 hours after ovulation when fertilization is most likely

Implantation timing – Normally occurs about day 6 after ovulation

Conceptus – A general term for all products of conception: embryo/fetus, placenta, and membranes

Embryonic folding – Process by which the embryonic disc folds around the yolk sac to form the primitive gut

Primitive gut – The early embryonic tube formed from the yolk sac that becomes the digestive tract

Thyroid and parathyroid glands – Derived from endoderm in the pharyngeal region

Epidermis – Derived from ectoderm and forms the outer skin layer

CNS (central nervous system) – Derived from ectoderm via the neural tube

Skeletal muscles – Derived from mesoderm

Salivary glands – Primarily derived from ectoderm

Digestive mucosa – Derived from endoderm

Smooth muscle – Derived from mesoderm

Skeleton – Derived from mesoderm

Gonads – Derived from mesoderm

Dermis – Derived from mesoderm

Parathyroid gland – Derived from endoderm

Digestive glands – Derived from endoderm

Teratogen

An agent or factor that causes birth defects during prenatal development.

Mutation

Any change in the DNA sequence or chromosome structure that may alter organismal function or structure.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate properly during meiosis, causing abnormal chromosome numbers.

Aneuploidy

Condition of having an abnormal number of chromosomes, either extra or missing.

Trisomy

Having three copies of a particular chromosome.

Monosomy

Having only one copy of a chromosome from a homologous pair.

Down syndrome

A disorder caused by trisomy 21, characterized by intellectual disability, flat face, short stature, and other physical features.

Turner syndrome

A disorder caused by monosomy X (only one X chromosome), characterized by short stature, infertility, and webbed neck.

Klinefelter syndrome

A disorder in males caused by an extra X chromosome (XXY), resulting in infertility, small testes, and gynecomastia.

Triplo X syndrome

A condition in females characterized by three X chromosomes (XXX).

Foramen ovale

A hole in the fetal heart's interatrial septum allowing blood to bypass the lungs.

Ductus arteriosus

A fetal blood vessel connecting the pulmonary artery to the aorta to bypass the lungs.

Ductus venosus

A fetal blood vessel that allows oxygenated blood from the umbilical vein to bypass the liver.

Umbilical arteries

Vessels carrying deoxygenated blood from the fetus to the placenta, originating from the internal iliac arteries.

Umbilical vein

Vessel carrying oxygenated blood from the placenta to the fetus.

Placenta

A disc

Amnion

The innermost fetal membrane that encloses the amniotic cavity filled with fluid.

Chorion

The outer fetal membrane that encloses the amnion and contributes to placenta formation.

Uterine milk

Nutrient

Premature infant

A baby born before 37 weeks of gestation, often with underdeveloped systems.

Neonate

An infant in the first 4 weeks after birth.

Presbyopia

Age

Osteoporosis

Severe loss of bone density leading to fragile bones and increased fracture risk.

Osteopenia

Mild to moderate loss of bone tissue, precursor to osteoporosis.

Osteoarthritis

Degenerative joint disease causing stiffness and joint pain.

Senescence

Degeneration and decline in function of cells or organ systems with aging.

Replicative senescence

The decline in a cell’s ability to divide due to telomere shortening.

Telomere

Protective caps at the ends of chromosomes that shorten with each cell division.

Intrinsic aging

Natural, genetically programmed aging process.

Extrinsic aging

Aging due to environmental factors such as UV exposure.

Presbycusis

Age

Benign prostatic hyperplasia (BPH)

Noncancerous enlargement of the prostate gland common in older men.

Immune system aging

Decline in immune function due to thymus involution and decreased immune surveillance.

Exercise benefits

Reduces risk of diabetes and hypertension, maintains muscle strength, and improves lifespan.

Hair graying

Due to the loss of melanocytes in hair follicles.