🌸 Reproduction &amp; Endocrinology

Reproduction

The biological process by which organisms produce offspring, asexual or sexual.

Asexual Reproduction

One parent produces genetically identical offspring, through binary fission, budding or fragmentation.

Sexual Reproduction

Two gametes fuse, mixing genetic material to produce varied offspring.

Gametes

Haploid sex cells, sperm and egg, that fuse at fertilisation.

Male Reproductive System

Testes make sperm and testosterone, with ducts and glands that deliver semen.

Female Reproductive System

Ovaries release eggs and hormones; the uterus nurtures the developing embryo.

Menstrual Cycle

A roughly 28-day cycle in which the uterine lining builds and sheds in response to hormones.

Puberty

The stage when sex hormones trigger sexual maturation and reproductive capability.

Pregnancy

The development of a fetus in the uterus lasting about 40 weeks in humans.

Contraception

Methods that prevent pregnancy, including barriers, hormones and sterilisation.

Hormones

Chemical messengers released into the blood that regulate growth, metabolism and reproduction.

Endocrine Glands

Pituitary, thyroid, adrenals, pancreas and gonads secrete hormones directly into the blood.

Insulin and Glucagon

Pancreatic hormones that lower and raise blood sugar.

Adrenaline

A hormone from the adrenal glands that prepares the body for fight or flight.

Plant Reproduction Overview

Plants reproduce sexually by seeds and spores, or asexually by runners, tubers and cuttings.

Intermediate topics (18)

Spermatogenesis

Production of sperm in the seminiferous tubules by meiosis and differentiation.

Oogenesis

Development of egg cells in the ovary, with unequal division creating one large ovum and polar bodies.

Hormonal Control of the Menstrual Cycle

FSH, LH, oestrogen and progesterone interact in feedback loops to time ovulation and menstruation.

Ovulation

Release of a secondary oocyte from the ovary triggered by a surge in luteinising hormone.

Fertilisation Process

The sperm penetrates the egg, triggering the cortical reaction that blocks other sperm.

Implantation

The blastocyst embeds in the uterine lining about a week after fertilisation.

Pregnancy Hormones

hCG maintains the corpus luteum early on, then the placenta produces progesterone and oestrogen.

Parturition

Positive feedback between oxytocin and uterine contractions drives childbirth.

Lactation

Prolactin stimulates milk production and oxytocin triggers milk let-down.

Negative Feedback in Endocrine Control

Rising hormone levels inhibit further secretion, as with thyroxine and TSH.

Positive Feedback

An effect amplifies its own cause, as in labour contractions and the LH surge.

Hypothalamic-Pituitary Axis

The hypothalamus controls the anterior pituitary, which signals target glands through trophic hormones.

Thyroid Hormones

Thyroxine and triiodothyronine regulate metabolic rate, growth and development.

Adrenal Cortex Hormones

Cortisol regulates stress and glucose; aldosterone controls salt balance.

Growth Hormone

A pituitary hormone stimulating growth of bone and muscle and affecting metabolism.

Melatonin

A pineal hormone that signals darkness and helps regulate sleep timing.

Infertility and IVF

In vitro fertilisation combines egg and sperm outside the body and transfers the embryo to the uterus.

Sexually Transmitted Infections

Infections like chlamydia and HIV spread through sexual contact, prevented by barrier methods and testing.

Advanced topics (21)

Steroid and Peptide Hormone Mechanisms

Steroid hormones cross membranes and alter transcription; peptide hormones bind surface receptors and activate second messengers.

Hormone Receptor Regulation

Cells adjust receptor number and sensitivity, causing resistance or hypersensitivity.

Pulsatile Hormone Secretion

GnRH and other hormones are released in pulses whose frequency encodes signalling information.

Sex Steroid Biosynthesis

Cholesterol is converted stepwise by enzymes like aromatase into androgens and oestrogens.

Endocrine Disruptors

Chemicals such as BPA mimic or block hormones, disturbing development and reproduction.

Reproductive Strategies Across Taxa

Hermaphroditism, parthenogenesis and sequential sex change appear across animals and plants.

Parthenogenesis

Development of an egg without fertilisation, found in some insects, reptiles and fish.

Meiotic Recombination Hotspots

PRDM9 directs where crossing over happens, shaping genome diversity.

Sperm Capacitation and Acrosome Reaction

Sperm undergo biochemical changes that let them penetrate the egg's protective layers.

Zona Pellucida and Egg Activation

Egg coat proteins bind sperm and calcium waves activate development after fusion.

Endocrine Tumours

Overgrowth in hormone-secreting glands can produce excess hormones, as in pituitary adenomas.

Polycystic Ovary Syndrome

A common endocrine disorder involving ovulation problems, androgen excess and metabolic disturbance.

Plant Hormone Crosstalk in Reproduction

Interacting auxin, gibberellin and cytokinin signals control flower, fruit and seed development.

Pheromones in Reproduction

Chemical signals synchronise mating, such as moth sex attractants.

Contraceptive Pharmacology

Hormonal contraceptives suppress ovulation using synthetic oestrogen and progestins.

Reproductive Ageing

Declining egg quantity and quality leads to menopause and falling fertility.

Genomic Imprinting in Placenta

Imprinted genes regulate placental growth, balancing parental interests in resource allocation.

Assisted Reproductive Technology Ethics

Debates on embryo selection, donor anonymity and access shape ART regulation.

Circadian Endocrinology

Hormone levels follow daily cycles, with cortisol peaking in the morning and melatonin at night.

Evolution of Placentation

Viviparity and the placenta evolved independently many times across vertebrates.

Endocrine System Modelling

Mathematical models of feedback loops predict hormone dynamics and treatment responses.