Human Development Stages

Study Notes

Puberty in females occurs from 11 to 13 years, while in males, it occurs from 12 to 14 years.
During puberty, there is a period of rapid growth followed by a period of slower growth.
Adult stature is reached in females by 17 to 18 years and in males by 19 to 20 years.

Prenatal development begins at fertilization, where a sperm attaches to a secondary oocyte, and their contents combine.
The secondary oocyte is surrounded by the corona radiata and zona pellucida.
The sperm's acrosome binds to a receptor on the zona pellucida, initiating the acrosomal reaction.
The first sperm cell to penetrate the zona pellucida binds to a receptor on the oocyte, causing depolarization, which prevents additional sperm from attaching.
The zona pellucida degenerates, preventing further sperm from attaching.

The syncytiotrophoblast surrounds maternal blood vessels, forming cavities called lacunae that contain maternal blood.
Cords of cytotrophoblast surround the syncytiotrophoblast and lacunae, and embryonic mesoderm and blood vessels grow into these cords.

Branches from the cords of cytotrophoblasts sprout into chorionic villi that protrude into the lacunae.
The entire embryonic structure facing the maternal tissues is called the chorion.
As the placenta matures, the cytotrophoblast disappears, and the embryonic blood supply is separated from the maternal blood supply by only the embryonic capillary wall, a basement membrane, and a thin layer of syncytiotrophoblast.

The respiratory system and cardiovascular system undergo changes, including the closure of the foramen ovale and ductus arteriosus.
The umbilical vein and arteries degenerate, and the digestive system begins to function.
The liver does not produce adult bilirubin for the first two weeks, and lactose can be digested, but other food must be gradually introduced.
Oxytocin stimulates milk letdown in the breast.

Atherosclerosis is the deposit and hardening of materials in lesions in large and medium-sized arteries, leading to arteriosclerosis, thrombus, and/or embolus.
Progressive aging of cells occurs due to exposure to toxic substances, such as free radicals, which can react with and alter cells.
Poor diet may lead to vitamin deficiency, and a decrease in ATP production may occur due to mitochondrial DNA mutations.
The immune system becomes less responsive to outside antigens but more responsive to self-antigens.
A genetic component contributes to longevity, and progeria is a genetic trait causing premature aging.

Genetics is the study of heredity, and Mendelian genetics is the study of how genetic traits are passed on to offspring.
Genotype refers to the genes an organism has for a given trait, while phenotype refers to the expression of those genes as a trait.
Dominant and recessive alleles are alternate forms of genes, and dominant alleles mask the effects of recessive alleles.
Homozygous refers to having two of the same alleles for a trait, while heterozygous refers to having one dominant and one recessive allele for a trait.

Chromosomes contain thousands of genes and are found in discrete sections of DNA.
Autosomal and sex chromosomes are the two types of chromosomes, and diploid refers to having two copies of chromosomes, while haploid refers to having one copy, only in gametes.
Karyotype is a map of chromosomes.
Homologous pairs of chromosomes are pairs where one is from the father and the other is from the mother, and locus refers to the location of a gene on a chromosome.