SCIENCE 3RD QTR

REPRODUCTIVE SYSTEM

MALES

Testes

• Produce testosterone and sperm, which are essential hormones and cells for male reproduction.

• They are the principal reproductive organ in males, crucial for fertility and male characteristics.

• Composed of three main parts:

  • Seminiferous Tubules: Coiled tubes inside the testes where sperm is produced from immature sperm cells.

  • Leydig Cells: Surround the seminiferous tubules and create testosterone, affecting libido, bone density, and muscle mass.

  • Sertoli Cells: Support developing sperm and regulate their formation, providing a barrier in the testes.

MALE STRUCTURE AND FUNCTION

• Scrotum: Protects the testes and maintains a cooler environment necessary for optimal sperm production.

• Ducts (Pathways for Sperm):

  • Epididymis: A tightly coiled tube where sperm mature and are stored temporarily; crucial for sperm functionality.

  • Vas Deferens: A muscular tube that transports mature sperm from the epididymis to the urethra during ejaculation.

  • Urethra: A tube that serves as a passage for urine from the bladder and for semen during ejaculation.

• Glands:

  • Seminal Vesicle: Produces a nutrient-rich fluid (containing fructose, ATP, and prostaglandins) for sperm nourishment.

  • Prostate Gland: Produces fluids that help nourish sperm and protect against bacterial infection.

  • Bulbourethral Glands: Produce a lubricating fluid to prepare the urethra before ejaculation.

• Penis: The organ responsible for sexual intercourse and the delivery of sperm; has tissues that fill with blood to enable an erection.

• Semen: A combination of sperm and gland secretions, typically 2.5-5 ml per ejaculation, with a healthy sperm concentration of 50-100 million sperm per milliliter.

FEMALES

FEMALE REPRODUCTIVE ORGANS

• Ovaries: Produce estrogen and progesterone, hormones that regulate the menstrual cycle and sex characteristics like breast development.

• Ovulation: The process of releasing an egg from the ovary, usually occurring around the midpoint of the menstrual cycle triggered by hormones.

• Oviduct (Fallopian Tube): Transports the egg to the uterus; fertilization occurs here if sperm are present.

• Cervix: The lower section of the uterus that opens to allow sperm to enter and expands during childbirth.

• Vagina: The canal connecting the outside of the body to the uterus; the site for sexual intercourse and the birth passage for babies.

MENSTRUAL CYCLE

• Lasts about 28 days and has four phases:

  • Menstrual Phase (3-7 days): Shedding of the uterine lining.

  • Follicular Phase (13-14 days): Ovarian follicles grow due to hormonal stimulation, leading to the production of an egg.

  • Ovulation (16-32 hours): The mature follicle releases an egg, triggered by hormonal surges.

  • Luteal Phase (14 days): The remnants of the follicle transform into the corpus luteum, which produces hormones needed for any potential pregnancy.

ENDOCRINE SYSTEM

FUNCTIONS AND REGULATIONS

• Hormones: Chemical messengers released into the bloodstream, impacting processes like growth, metabolism, and mood.

• Hormone Regulation: Hormone levels are balanced through mechanisms such as kidney excretion, liver breakdown, and feedback systems to maintain homeostasis.

FEEDBACK SYSTEMS

• Negative Feedback: Reduces hormone output to restore balance (e.g., blood sugar regulation).

• Positive Feedback: Increases hormone production to achieve desired effects (e.g., oxytocin release during childbirth contractions).

ENDOCRINE GLANDS

• Hypothalamus: Connects the nervous and endocrine systems; it regulates body functions such as hunger and body temperature.

• Pituitary Gland: Known as the Master Gland, it controls other endocrine glands by releasing hormones like FSH and LH, which are crucial for reproduction.

• Thyroid Gland: Regulates metabolism and produces calcitonin to lower blood calcium levels, influencing growth and development.

• Pancreas: A gland that produces insulin (lowers blood sugar) and glucagon (raises blood sugar) to regulate glucose levels.

• Parathyroid Gland: Controls blood calcium levels through parathyroid hormone (PTH), which promotes healthy bone growth.

• Thymus: Essential for the immune system, it produces thymosin which assists in T cell maturation.

• Adrenal Glands: Located atop the kidneys, they produce hormones such as adrenaline and cortisol, which help manage stress. Manages fight or flight response.

• Ovaries and Testes: The ovaries secrete estrogen and progesterone for female reproduction, while the testes produce testosterone for male characteristics and sperm production.

COMMON HORMONAL DISORDERS

• Goiter: Swelling of the thyroid, often due to iodine deficiency or overactivity, affecting thyroid function and leading to hyperthyroidism or hypothyroidism.

• Hyperthyroidism: An overactive thyroid causing excess hormone production, potentially leading to symptoms like weight loss and anxiety (Faster Metabolism).

• Hypothyroidism: An underactive thyroid with insufficient hormone levels, often resulting in fatigue and weight gain (Slower Metabolism).

• Gigantism: Caused by overproduction of growth hormone from the pituitary gland, resulting in unusually large stature.

• Dwarfism: Caused by insufficient growth hormone, leading to shorter stature; can be due to genetic conditions or endocrine issues.

NERVOUS SYSTEM

STRUCTURE AND FUNCTION

• Nervous System Overview: Composed of the central nervous system (CNS) and the peripheral nervous system (PNS), responsible for processing sensory information and coordinating responses.

• Central Nervous System (CNS): Consists of the brain and spinal cord, which control and integrate sensory and motor functions.

• Peripheral Nervous System (PNS): Includes nerves that transmit signals between the CNS and the body, facilitating reflexes and voluntary movements (Carries info to and from the brain).

NEURONS

• Neuron (Nerve Cell): The basic functional unit of the nervous system that communicates through electrochemical signals.

• Parts of a Neuron:

  • Soma (Cell Body): Contains the nucleus and organelles required for the cell's survival.

  • Dendrites: Branch-like projections that receive signals from other neurons and transfer them to the soma (carries impulses towards the cell body).

  • Axon: A long fiber that transmits signals away from the cell body; often encased in myelin for faster signal transmission.

NEURON TYPES

• Sensory Neurons: Transmit signals from sensory receptors to the CNS; responsible for sensations including touch and sight.

• Interneurons: Located within the CNS, they process information between sensory inputs and motor outputs, crucial for reflex actions.

• Motor Neurons: Convey impulses from the CNS to muscles and glands, enabling bodily movements and responses.

NERVE IMPULSES AND SIGNALING

• Nerve Impulse: An electrochemical signal traveling along the axon, involving various phases of depolarization and repolarization.

• Synapse: The junction where two neurons communicate using neurotransmitters, facilitating signal transmission within the nervous system.

BIOMOLECULES

FOUR MAJOR BIOMOLECULES

• Carbohydrates:

  • Serve as a primary energy source, containing carbon, hydrogen, and oxygen.

  • Monomer: Monosaccharides (like glucose).

  • Types:

    • Monosaccharides: Simple sugars (consists of glucose, fructose, and galactose).

    • Disaccharides: Formed by the combination of two monosaccharides, examples include sucrose (glucose + fructose) and lactose (glucose + galactose) maltose (glucose + glucose).

      Polysaccharides: Complex carbohydrates composed of long chains of monosaccharide units, such as starch, glycogen, and cellulose.

    • Disaccharides: Two monosaccharides linked together (e.g., sucrose).

    • Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen).

• Lipids:

  • A diverse group of hydrophobic substances, including fats, oils, and hormones.

  • Monomer: Glycerol and fatty acids.

  • Roles: Energy storage, membrane formation, insulation, and signaling.

• Proteins:

  • Made of amino acids joined by peptide bonds; perform various functions based on their structure.

  • Monomer: Amino acids (20 different types and there are 8-9 amino acids that the human body can not produce).

  • Functions: Include enzymes, structural components (collagen), immune responses (antibodies), and signaling molecules (hormones).

• Nucleic Acids:

  • Macromolecules essential for genetic information storage and transfer.

  • Monomer: Nucleotides, which consist of a nitrogen base, sugar, and phosphate group.

  • Roles: DNA stores genetic instructions, while RNA plays a role in protein synthesis and gene expression.

DNA AND RNA

TYPES

• DNA:

  • Sugar: Deoxyribose.

  • Bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G) in pairs (A-T, C-G).

• RNA:

  • Sugar: Ribose.

  • Bases: Adenine (A), Uracil (U), Cytosine (C), Guanine (G) (uracil replaces thymine in RNA).

PROTEIN SYNTHESIS

Process Sequence:

1. DNA Replication: The DNA strand duplicates prior to cell division.

2. Transcription: A specific segment of DNA is copied into mRNA inside the nucleus.

3. Translation: Proteins are synthesized at ribosomes using mRNA and transfer RNA (tRNA) that brings the appropriate amino acids according to codon sequences.

4. Codon: A triplet of nucleotides on mRNA that pairs with complementary tRNA anticodons.

CHROMOSOMAL MUTATIONS

CHROMOSOME STRUCTURE

• Chromosomes: Coiled structures of DNA wrapped around proteins; vital for accurate DNA distribution during cell division.

TYPES OF MUTATIONS

• Numerical Mutations:

  • Occur due to missteps in meiosis or mitosis that alter chromosome number.

  • Examples:

    • Trisomy: Presence of an extra chromosome (e.g., Down syndrome).

    • Monosomy: Absence of one chromosome (e.g., Turner syndrome).

    • Polyploidy: Presence of extra sets of chromosomes, common in plants but typically detrimental in animals.

• Structural Mutations:

  • Changes that affect chromosome structure, often due to breakage and rejoining of DNA strands.

  • Examples:

    • Translocation: Movement of a chromosome segment to another chromosome, which can cause genetic disorders.

    • Deletion: The loss of segments of chromosomes, leading to syndromes like Cri Du Chat syndrome.

    • Duplication: Presence of extra copies of chromosome segments, contributing to conditions like Charcot-Marie-Tooth disease.