BISC 113 Chapter 3

Human Development

Human Development

The process by which an individual grows and matures from a single cell embryo inside a mother’s womb to a baby that can survive on its own.

Conjoined Twin

Identical twins whose bodies are physically attached at some location.

Cell

The most basic unit of life

Embryogenesis

The development of cells into embryos and bodies that are able to perform the tasks necessary for life.

Cell Theory

The realization that all living organisms are made of cells; it was first proposed in 1839 by Matthias Schleiden and Theodor Schwann.

Organelle

Specialized structure in eukaryotic cells.

Nucleus

Most prominent organelle; houses chromosomes

Cell Membrane

Outer cell boundary; controls movement of food molecules and waste products.

Mitochondrion

Organelle responsible for extracting energy from food molecules

Cytoplasm

Cytosol and organelles together

Cytosol

Viscous substance where molecules are dissolved and organelles are embedded.

Cytoskeleton

Maintains shape of cell and positions of its organelles.

Lysosome

Digests waste materials and worn-out organelles.

Golgi Apparatus

Place where proteins acquire final structure.

Smooth Endoplasmic Reticulum (SER)

Membrane folds that handle synthesis of fats and lipids and break down toxic substances.

Ribosome

Site of protein synthesis; found free in cytoplasm and also studding RER surface.

Rough Endoplasmic Reticulum (RER)

Membrane folds that produce proteins essential for cell structure.

Chromosomes

Structures that contain most of a cell’s genetic information.

Microfilaments

Versatile, thin, and strong; help pinch the cell membrane so that cells may divide in two.

Microtubules

Hollow rods that determine cell shape and help with cell movement.

Intermediate Filaments

Strong fibers that help strengthen cells and reinforce the physical connections of cells to each other.

Gamete

Sex cell; the product of sexual reproduction all organisms undergo.

Meiosis

A special type of cell division that produces eggs or sperm.

What are the steps of Meiosis I and II?

Meiosis I:

• Interphase - chromosomes replicate, all organelles continue to function, and the cell increases in size (chromosomes are loosely packaged and are hard to see individually even with a powerful light microscope)

• Prophase I - chromosomes get shorter and thicker, line up with their homologues, and the membrane surrounding the nucleus comes apart, leaving the chromosomes in the cytoplasm

• Metaphase I - specific proteins associated with the fibers of the mitotic spindle pull the chromosomes toward both poles, pairing them to line up in single file down the middle of the cell

• Anaphase I - paired chromosomes separate and move to opposite poles using the shrinking microtubules as tracks; there’s now a haploid set of chromosomes on each side of the cell

• Telophase I and cytokinesis - cell pinches and divides in two as each new cell gets a complete set of organelles and chromosomes

Meiosis II

• Prophase II - chromosomes still in compact form attach to the newly formed spindle

• Metaphase II - chromosomes are captured by one or more microtubules from each side and line up in a single file in the middle of the cell

• Anaphase II - two chromatids of each chromosome detach from each other and move to opposite ends of the cell; each half of the cell has a complete haploid set of chromosomes and each chromosomes is composed of a single chromatid

• Telophase II and cytokinesis - nuclear membrane reforms and encloses the chromosomes which return to their relaxed, decondensed form for cytokinesis to pinch the cells in two

Homologue

One in a pair of chromosomes

Testis

Male sex organ where sperm are produced

Ovary

Female sex organ where eggs are produced

Diploid Cell

Cell with two complete sets of chromosomes.

Haploid Cell

A cell with just one set of chromosomes.

Interphase

The stage in cell division when cells prepare materials that will be necessary for meiosis or mitosis to occur.

Prophase I

In meiosis, the stage in the first found of cell division when the chromosomes become shorter and thicker and line up with their homologues.

Spindle

Formed from the microtubules of the cytoskeleton, this is a structure that helps distribute chromosomes to new cells.

Metaphase I

In meiosis, the stage in the first round of cell division when paired chromosomes line up in single file down the middle of the cell.

Anaphase I

In meiosis, the stage in the first round of cell division when paired chromosomes separate and move to opposite poles, leaving a haploid set of chromosomes on each side of the cell.

Telophase I and Cytokinesis

In meiosis, the stage in the first round of cell division when the cell pinches and divides in two; each new cell has a complete set of organelles and chromosomes.

Chromatid

One of two copies of the DNA and proteins that make up a replicated chromosome; replicated chromosomes are composed of two chromatids.

Prophase II

In meiosis, the stage in the second round of cell division when chromosomes, still in their compact form, attach to the newly formed spindle.

Metaphase II

In meiosis, the stage in the second round of cell division when chromosomes line up in single file in the middle of the cell.

Anaphase II

In meiosis, the stage in the second round of cell division when two chromatids of each chromosome detach from each and move to opposite ends of the cell; each half of the cell has a complete haploid set of chromosomes.

Telophase II

In meiosis, the stage in the second round of cell division when nuclear membrane reforms and encloses the chromosomes.

Cytokinesis

The stage in cell division where the cells are pinched in two

Fertilization

The process of a sperm cell from the father being fused with an egg cell from the mother.

Zygote

A one-celled embryo produced as a result of fertilization.

Cleavage

The start of embryogenesis when the cells divide into new cells.

Embryo

The earliest stage of development

Mitosis

A type of cell division during which all of the chromosomes in a cell are copied or replicated, and each new cell receives genetic information identical to the parent cell.

Mitosis involves one round of cell division compared to meiosis. Explain the process of mitosis.

1. Interphase: chromosomes replicate and the cell increases in size

2. Prophase: chromosomes become shorter and wider and the mitotic spindle forms

3. Late prophase: the spindle fibers attach to the chromosomes

4. Metaphase: chromosomes line up in a single file

5. Anaphase: chromatids of each chromosome separate; one full self, composed of single chromatids that move to one pole and another to the opposite pole

6. Telophase & Cytokinesis: a nucleus reforms in each half of the cell, enclosing the chromosomes as the cell pinches and divides into two

Placenta

An organ that connects a developing fetus to the mother’s uterine wall and provides for an exchange of nutrients and waste elimination.

Embryonic Stem Cell

Cell that can produce any type of cell in the body.

Gastrulation

A stage in embryonic development in which cells and tissues move to new locations, where they will grow into organs.

Neural Tube

The tissue that starts from a flat sheet of cells and rolls up, ultimately becoming the brain and spinal cord.

Differentiation

The change from the cells that have unlimited potential to cells that are specialized.

Gene Expression

The process during which the information encoded in genes is used.

Muscle Cell (gene expression)

• Highly active A gene

• Silent B gene

• Slightly active C gene

Skin Cell (gene expression)

• Silent A gene

• Highly active B gene

• Slightly active C gene

Nerve Cell (gene expression)

• Moderately active A gene

• Silent B gene

• Moderately active C gene

Uterus

Mother’s womb

Neurulation

Formulation of the earliest stages of the central nervous system.

Fetus

The stage of development that follows the embryo

Ultrasound

A device that relies on high-frequency sound waves to send back images of internal organs.

Explain the order of what develops from week 1 to week 8 of pregnancy.

Week 1: cleavage produces cells that will form embryo + chorion

Week 2: embryo becomes the size of a period, implants in the wall of the uterus; gastrulation and cell specialization occur

Week 3: earliest stage of central nervous system form along with the start of heart development

Week 4: heart development continues, limb buds appear, and the embryo is barely larger than 2 millimeters

Week 5: nose, eyes, and ears appear

Week 6 & 7: fingers and toes are evident and the embryo has a skeleton made of cartilage

Week 8: embryo is approximately 1.5 inches long, bone begins replacing cartilage and all organ systems are developing

Explain the ordinal development of the fetus from month 3 to month 9

Month 3 (12-15 weeks): can discern the gender of the fetus and fingernails begin to form

Month 4 (16-19 weeks): approximately 6 inches long, weighing 6 ounces; skeleton is visible via ultrasound, eyelashes, eyebrows, and hair are present

Month 5 (20-23 weeks): stethoscope on mother’s abdomen detects fetal heartbeat which the mother can feel

Month 6 & 7 (24-31 weeks): organ systems continue to mature and the eyes open

Month 8 & 9 (32-39 weeks): fetus increases in size, lungs mature, body hair disappears; typical newborn weighs around 7 pounds and is 20 inches long

Fetal alcohol spectrum disorder (FASD)

Encompasses a range of health problems experienced by children who were exposed to alcohol prenatally.

Fetal Alcohol Syndrome (FAS) Symptoms

In most severe cases, symptoms may include poor growth, abdominal facial features, hyperactivity, poor reasoning skills, vision problems, hearing problems, and intellectual disabilities.

Cervix

The lower end of the uterus

What are the 3 stages of labor and delivery in pregnancy?

Stage 1: uterine contractions pull the lower part of the uterus up toward the fetus’ head and push the fetus down

Step 2: strong contractions every minute as the mother experiences the urge to push and the baby emerges

Step 3: the placenta is delivered

Amnion

Sac in which the embryo is suspended.