Human Body Systems: Respiratory, Circulatory, Reproductive, and Nervous
Respiratory System
Types of Respiration
External Respiration: Exchange of gases between the atmosphere and the blood.
Internal Respiration: Exchange of gases between the blood and the body’s cells.
Breathing
Breathing: Mechanical movement of air into and out of the lungs.
Respiratory System Functions
- Gas exchange
- Gas delivery to body cells
- CO2 expulsion from the body
- Oxygen utilization in cells to produce ATP
Air Pathway
Nasal passages, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, blood, cells.
Inhalation and Exhalation
Inhalation: The act of taking air into the lungs. The diaphragm contracts, causing the lungs to expand and allowing air to move in.
Exhalation: The diaphragm relaxes and returns to its normal resting position.
Respiratory System Components
Bronchi: Tubes that lead to the lungs.
Alveoli: CO2 and oxygen are exchanged between air and blood.
Lungs: Where gas exchange takes place.
Circulatory System
Functions
Exchange of oxygen, nutrients, and wastes.
Components
Blood, heart, blood vessels, and lymphatic system.
Blood
Transports important substances through the body and contains living cells. Composed of: plasma, red blood cells, platelets, white blood cells.
Key Circulatory Structures
Aorta: Connects oxygenated blood to the body.
Pacemaker: Sends out signals that tell the heart muscle to contract.
Pulse: Alternating expansion and relaxation of the artery wall caused by contraction of the left ventricle.
Blood Pressure: A measure of how much pressure is exerted against the vessel walls by the blood.
Blood Vessels: Arteries, capillaries, veins.
Blood Pathway
Enters the heart through the vena cava, then goes to the Right Atrium (tricuspid valve), then to the Right Ventricle (pulmonary valve), pulmonary arteries, enters the lungs and turns red, enters the Left Side: pulmonary veins, Left Atrium (mitral valve), Left Ventricle, aorta, and then goes to the body.
Heart Contraction and Relaxation
Contraction: Systole.
Relaxation: Diastole.
Coronary Arteries
Supply oxygen to the heart muscle.
Heart Diseases
Tachycardia, hypertension.
Reproductive System
Asexual Reproduction
Offspring arise from a single parent.
Types of Asexual Reproduction
- Budding: New organism grows by mitosis (e.g., yeast).
- Fission: Cell division where a prokaryotic organism grows and forms two identical cells (e.g., bacteria).
- Regeneration: Offspring grows from a piece of a parent (e.g., starfish).
- Vegetative Regeneration: Offspring grow from a part of the plant (e.g., potato).
Sexual Reproduction
Forming a new individual following the union of two gametes.
Male Reproductive System
Functions
- Produce sperm
- Deliver sperm to the vagina
Structures
Testes, penis, prostate gland, vas deferens, epididymis, urethra.
- Testes: Produce sperm, found in the scrotum.
- Epididymis: Stores sperm as they mature.
- Ductus Vas Deferens: Conducts and stores sperm.
- Urethra: Conducts sperm and urine out of the body.
- Penis: Serves as an organ of copulation.
Glands
- Seminal Vesicles: Provide energy for sperm.
- Prostate Gland: Neutralizes acidity in the urethra and the vagina.
- Cowper’s Gland: Contributes to seminal fluid.
Path of Sperm
- Formed in the seminiferous tubules of the testes.
- Mature and stored in the epididymis.
- Stored in the first part of the vas deferens.
- Enters the urethra just prior to ejaculation.
- Accessory glands add secretions to semen.
- Semen exits through the penis.
Hormones
GnRH, LH, FSH: stimulate testosterone production.
Female Reproductive System
Functions
- Produce ova
- Transfer sperm
- Prepare for pregnancy
Structures
- Ovaries: Produce eggs.
- Fallopian Tubes: Move egg toward uterus, site of fertilization.
- Uterus: Site of development.
- Cervix: Produces mucin, holds baby in the uterus.
- Vagina: Birth canal.
- Clitoris: Responsible for stimulating female orgasm.
Oocyte
Mature egg, stimulated by the ovary.
Hormone Control
- Pituitary Gland: Makes two hormones that act on the ovaries:
- FSH (Follicle Stimulating Hormone): Stimulates follicle maturation and estrogen production.
- LH (Luteinizing Hormone): Maintains the corpus luteum and progesterone production, increases on the day of ovulation.
- Ovary: Makes hormones that act on the endometrium:
- Estrogen: Made by the follicle.
- Progesterone: Made by the corpus luteum.
Corpus Luteum
Produces progesterone and some estrogen, breaks down, no longer producing these hormones.
Menstrual Cycle
- Flow (Menstruation): Days 1-5.
- Follicular: Follicles develop in ovaries, endometrium is restored; estrogen; days 6-13.
- Ovulation: Oocyte bursts from ovary; day 14.
- Luteal: Corpus luteum forms, uterine lining thickest; estrogen and progesterone; days 15-28.
Menstruation
Progesterone levels decrease.
Fertilization
Process of a sperm joining with an egg.
A sperm enters the ovum, and the nuclei combine to form one with chromosomes.
Steps of Fertilization
- Sperm contacts the egg.
- Sperm or its nucleus enters the egg.
- Egg becomes activated, and developmental changes begin.
- Sperm and egg nuclei fuse.
Early Development
Ovum: Egg cell (female gamete).
Cleavage: Process of cell division during development.
Embryo: An organism in an early stage of development.
Morula: A solid ball of cells formed from cleavage.
Blastula: A hollow ball of cells with an in-pushing and three layers.
Early Development Stages
- The zygote moves through the oviduct propelled by involuntary smooth muscle contractions and by cilia lining the oviduct.
- The zygote undergoes its first mitosis and cell division.
- By the third day, the embryo leaves the oviduct and enters the uterus, now described as a morula.
- By the fifth day, it is called a blastocyst.
Pregnancy
First Trimester
- Organ systems begin to develop.
- At 8 weeks, the embryo is called a fetus.
- At the end, the fetus can move arms and fingers.
Second Trimester
- Period of growth.
- Fetal heartbeat might be heard.
- Hair forms.
Third Trimester
- Fat accumulates under the skin.
- New nerve cells form.
Nervous System
Neuron
Specialized cells that help gather information about the environment.
Types of Neurons
- Sensory Neurons: Send impulses from receptors in the skin and sense organs to the brain and spinal cord.
- Interneurons: Carry the impulse to motor neurons.
- Motor Neurons: Carry impulses away from the brain and spinal cord to a gland or muscle, resulting in a response.
Divisions of the Nervous System
- Central Nervous System (CNS): Mostly made up of interneurons.
- Function: Coordinates all of the body’s activities, relays messages, processes information, and analyzes responses.
- Brain: Maintains homeostasis.
- Cerebrum: Carries out thought processes involved with learning, memory, and language.
- Cerebellum: Controls balance and coordination.
- Brain Stem:
- Medulla Oblongata: Relays signals between the brain and the spinal cord, helps control breathing rate, heart rate, and blood pressure.
- Pons: Relays signals between the cerebrum and the cerebellum.
- Hypothalamus: Located between the brain stem and the cerebrum, essential for maintaining homeostasis.
- Spinal Cord: A nerve column that extends from the brain to the lower back. Reflexes are processed in the spinal cord.
- Peripheral Nervous System (PNS): Includes all neurons that are not part of the CNS, including sensory neurons and motor neurons.
- Somatic Nervous System: Relays information from external sensory receptors to the CNS, and motor nerves relay information from the CNS to skeletal muscles. Usually voluntary.
- Autonomic Nervous System: Carries impulses from the CNS to the heart and other internal organs. The body responds involuntarily.
- Sympathetic Nervous System: More active in times of emergency or stress.
- Parasympathetic Nervous System: Most active when the body is relaxed.