Circulatory System: Heart, Blood, and Vessels

• The circulatory system, also known as the cardiovascular system, transports nutrients, gases, wastes, and hormones.
• It is closely linked to the respiratory system, which is in charge of gas exchange.
• The circulatory system comprises the heart, blood, and blood vessels.

Types of Circulatory Systems

• An open circulatory system is found in invertebrates, like insects or mollusks, where blood vessels have gaps or openings.
• It requires less energy to pump blood, or in this case, hemolymph.
• A closed circulatory system is found in vertebrates, like mammals and birds, with blood flowing through vessels like the arteries and veins.
• Requires more energy to maintain blood pressure

The Heart

• The heart is a muscular organ about the size of your fist that pumps blood throughout the body.
• It is located at the center of the chest, between the lungs, slightly to the left.
• The right half contains deoxygenated blood, while the left half contains oxygenated blood.

Layers of The Heart

• The endocardium is the thin, innermost layer.
• The myocardium is the thick, muscular middle layer.
• The pericardium is a fibrous sac that surrounds the heart, holding it in place and containing a small amount of fluid to reduce friction.
• The epicardium is the outermost, protective layer.

Parts of the Heart

• Atria are the two upper chambers that receive blood.
• The left atrium receives oxygenated blood from the lungs via the pulmonary vein.
• The right atrium receives blood from the superior and inferior vena cava.
• Ventricles are the two lower chambers that pump blood.
• The left ventricle pumps blood to the aorta, which distributes it to the rest of the body.
• The right ventricle pumps blood to the pulmonary artery, which carries blood to the lungs.
• Valves separate the upper and lower chambers and prevent the backward flow of blood.
• The tricuspid valve is located between the right atrium and right ventricle.
• The pulmonary valve is located between the right ventricle and the pulmonary artery.
• The mitral valve is located between the left atrium and left ventricle.
• The aortic valve is located between the left ventricle and the aorta.

Blood: The Fluid of Life

• Blood delivers essential nutrients to the cells and accounts for 7-8% of total body weight.
• It is a connective tissue with plasma and three types of cells: red blood cells, white blood cells, and platelets.

Parts of the Blood

• Erythrocytes, or red blood cells (RBCs), lack a nucleus.
• The protein molecule “hemoglobin” carries oxygen, making the blood red.
• Leukocytes, or white blood cells (WBCs), are the cells of the immune system.
• WBCs are larger than RBCs and defend the body from diseases, outnumbered by RBCs by a ratio of 700:1.
• Thrombocytes, or platelets, are colorless cells that are smaller than both RBCs and WBCs.
• Platelets aid in clotting.
• Thrombocytopenia is when the number of platelets is too low
• Thrombocythemia is when the blood clots excessively
• Plasma comprises about 55% of the volume in the blood and is the liquid part.
• Formed elements (erythrocytes, leukocytes, and thrombocytes) make up about 45% of the volume.

Blood Vessels: The Alleys and Highways

• Blood flows through tubes called blood vessels.
• There are three kinds of blood vessels: arteries, veins, and capillaries.
• Arteries carry blood away from the heart and have thick and elastic walls that can withstand high pressure.
• The largest artery is the aorta, with the smallest being the arterioles.
• Arteries have no valves because of the high pressure and are always represented as red in diagrams.
• Veins return the blood towards the heart, and have thinner walls, but wider than arteries.
• The biggest veins are the superior and inferior vena cava, with the smallest being the venules.
• Veins have valves to ensure blood flows in one direction back to the heart and are always represented as blue in diagrams.
• Capillaries facilitate the exchange of materials between the body and blood cells, or between the blood and lung tissues.

Blood Circulation

• There are two pathways through which blood circulates in the body: pulmonary and systemic.
• Pulmonary circulation moves blood between the heart and lungs.
• The deoxygenated blood pathway is: Superior and Inferior Vena Cava, Right Atrium, Right Ventricle, Pulmonary Artery, Lungs.
• Systemic circulation moves blood between the heart and the rest of the body.
• The oxygenated blood pathway is: Lungs, Pulmonary Vein, Left Atrium, Left Ventricle, Aorta

Homeostasis

• The respiratory and circulatory system collaborate to maintain overall balance in body functions.
• The respiratory system provides oxygen for cellular respiration.
• The circulatory system transports oxygen to the cells, and carbon dioxide back to the lungs.

The Respiratory System

• Respiration is the exchange of gases between the cells and their environment.
• Oxygen that has been inhaled is distributed to all the cells of the body by the circulatory system.

The Lungs

• The lungs are the main organs of the respiratory system, which allows you to breathe.
• The right lung has three lobes, while the left lung has two because of the heart.

Parts of the Respiratory System

• The nasal cavity has two openings called nostrils, which clean and warm inhaled air.
• The coarse hairs filter some dust particles; the mucous membrane moistens the inhaled air; and the cilia are microscopic hairs that move back and forth.
• The pharynx is part of both the respiratory and digestive system, allowing both food and air to pass through.
• The larynx is also known as the voice box, holding the vocal cords, which produce sound.
• The glottis is the opening of the trachea, with the epiglottis preventing swallowed food from entering the lower respiratory tract.
• The trachea, also known as the windpipe, is a tube that lies in front of the esophagus.
• At the end of the trachea are two large hollow branches called bronchi.
• Inside each lung, the bronchi splits into smaller tubes, which then branch into smaller microscopic tubes called bronchioles.
• Each bronchiole opens into “air sacs” called alveoli, surrounded by a network of capillaries.
• Gas exchange takes place in the capillaries of the alveoli.
• During inhalation, the diaphragm contracts and moves downward.
• During exhalation, the diaphragm returns to its normal shape.
• The pressure change in the lungs caused by the movement of the diaphragm makes breathing possible.

Care for the Circulatory and Respiratory Systems

• Exercise regularly.
• Get enough rest.
• Eat the right kinds and amounts of food.
• Do not smoke.
• Breathe in fresh air.
• Practice deep breathing.
• Breathe with the mouth closed.
• Prevent the accumulation of carbon monoxide.
• Prevent air pollution.
• Regularly consult a physician.

Diseases and Disorders

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Heredity: Inheritance and Variation

• Genetics is the study of hereditary information.
• Heredity is the passing of characteristics from parent to offspring.
• Somatic cells, or body cells, are diploid, having two sets of 23 chromosomes (46 total).
• Somatic cells play no direct part in fertilization
• Sex cells, the egg and the sperm, have half the chromosome number of the somatic cells, meaning they are haploid.
• Sex cells are the cells that are directly involved in fertilization and are also known as gametes.

Sex Cells and Inheritance

• Gregor Mendel, an Austrian monk and botanist, performed experiments using garden pea plants to formulate his laws on inheritance.
• Traits are passed on through breeding factors (currently known as genes).
• Alleles are variations of the genes.
• The P generation (parental) are pure-bred parental plants (PP, pp).
• The F1 generation (first filial) are offspring from the parental generation, where 100% of plants have purple flowers (Pp).
• The F2 generation (second filial) are offspring from the first filial generation, where 75% of plants have purple flowers.
• Dominant traits express themselves more and require only one copy of the allele to be expressed.
• Take the first letter of the dominant trait and make it capital
• Recessive traits are hidden and require two copies of the allele to be expressed
• Take the letter of the dominant trait and make it lowercase.
• Homozygous dominant is a purebred dominant trait (PP).
• Heterozygous dominant is a hybrid dominant trait (Pp).
• Homozygous recessive is a purebred recessive trait (pp).
• Genotype is the genetic makeup of an organism.
• Phenotype is the observable traits of the organism (physical appearance).

Mendel’s Laws of Inheritance

• Law of Dominance: Traits come in pairs; one may be dominant over the other.
• Dominant traits mask the other trait.
• Dominant traits are represented by a capital letter.
• Recessive traits are hidden unless paired with another recessive allele.
• Law of Segregation: During meiosis, chromosome pairs separate during gamete formation.
• This ensures that the offspring inherit one allele from each parent.
• Law of Independent Assortment: Inheritance of one trait does not affect the other traits.
• Different genes separate independently during gamete formation.

Sex Determination

• Human females have two sex chromosomes of the same kind called an X chromosome (XX).
• In human males, the two sex chromosomes are not alike (XY).
• The sex chromosomes are the last pair of chromosomes, which determine biological determination.

Mendelian Inheritance

• Monohybrid inheritance involves one pair of contrasting characteristics.
• Determines the inheritance of alleles in a single gene
• The Punnett Square calculates the possibility of each genotype in the offspring.
• Genotypic ratio is the ratio of different gene combinations in the offspring.
• Example genotypic ration: 1:2:1
• (homozygous dominant, heterozygous dominant, homozygous recessive).
• Phenotypic ratio is the ratio of the different observable traits in the offspring.
• Example phenotypic ratio: 3:1
• (dominant, recessive)

Non-Mendelian Inheritance

• They do not follow simple Mendelian patterns.

• Traits do not segregate in accordance to Mendel’s laws.

• In incomplete dominance, the heterozygous individuals show a blend of both parental traits.

• In codominance, both the alleles are expressed equally.

• Multiple alleles: A trait is controlled by more than two alleles

• Polygenic inheritance: Multiple genes control a trait.

Sex-Related Inheritance

• Sex-linked traits are located in the sex chromosomes and are more likely to appear on X.
• Sex-influenced traits are expressed in both sexes, but more common in one than the other.
• Sex-limited traits are expressed in only one sex.