Describe four mechanisms that assist in the return of venous blood to the heart.

interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle

answerclassical conditioning;

ans.

in united states (us), the first leading cause of death for both women and men is heart diseases that leads to more than half of the deaths. heart diseases develop due to narrow arteries, buildup of plaque in blood capillaries that arises difficulties in blood flow.

the second leading cause of deaths in us is cancer that affects individuals of all ages. it develops due to uncontrolled growth and spread of tumor cells, which results in death if the not controlled or treated.

the third leading cause of deaths in us is copd or chronic obstructive pulmonary disease. it includes difficulty in breathing, chest infections, and persistent cough. smocking is a leading cause of copd and around 80% of copd deaths occur due to smoking.

thus, the correct answer is 'option). cancer, copd, and heart disease.'

phosphorus cycle

explanation:

the phosphorus cycle is the way that compounds of the element phosphorus, an essential nutrient, are recycled in the environment. plants absorb phosphorus compounds from the soil, and decaying organic matter, including both plant matter and animal droppings, returns it to the soil. phosphorus is a vital part of atp, the energy currency of all cells, and is vital to all forms of life.