Cell Theory: Introduction and Fertilization

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Published on May 15, 2024

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In this video I go over a brief introduction into cell theory, which states that all living things are composed of one or more cells, and in multicellular organisms, every cell is derived from a single cell inside a fertilized egg. More terms and definitions covered are listed below.

Timestamps:

Cell theory states all living things are composed of one or more cells: 0:00
Eukaryotic cells contain a nucleus and can be single-celled or multicellular. Prokaryotic cells are single-celled and do not contain a nucleus: 0:56
Every cell in a multicellular organism is derived from a single cell in a fertilized egg: 1:22
Fertilization or impregnation is the fusion of gametes to give rise to a new organism: 1:30
Sexual reproduction is the cycle of fertilization: 1:54
Insemination is the introduction of sperm into a female's reproductive system: 1:59
Pollination is the transfer of pollen (which produce gametes) from a male part of a plant to a female part: 2:06
Gamete or sex cell is a haploid cell that fuses with another haploid cell during fertilization: 2:23
Female is any individual that produces the larger type of gamete (ovum) and a male produces the smaller type (sperm): 2:38
Sperm and ovum fusing: 2:57
Ploidy is number of complete sets of chromosomes in a cell: 3:00
Sets of chromosomes refer to the number of maternal and paternal chromosome copies in each homologous chromosome pair: 3:13
Somatic (non-sex) cells, tissues, individual organisms: Ploidy level: monoploid (1 set), diploid (2 sets), triploid (3 set), etc.: 3:48
Polyploid refers to 3+ chromosome sets: 4:50
Homologous chromosomes or homologs are a set of one maternal and paternal chromosome that pair up during fertilization: 4:59
Haploid has 1 complete set of chromosomes for a diploid species; 2 sets for a tetraploid species: 5:27
Haploid cells in humans have 23 chromosomes; diploid cells have 46 chromosomes: 6:20
Haploid has 2 related definitions: a cell with half the number of chromosomes in somatic cells, and a cell with just 1 set of chromosomes, termed monoploid: 7:08
Zygote is a eukaryotic cell formed by a fertilization event between 2 gametes: 7:33
Zygote's genome is a combination of the DNA of each gamete: 7:44
Egg results from fertilization of an egg cell and contains the zygote from which an embryo develops: 7:53
Embryo is the early stage of development of a multicellular organism: 8:10
Fetus refers to 9+ weeks after conception in humans: 8:15
Male human embryo of 7 weeks old or 9 weeks gestational age: 8:38
Gestational age starts from the woman's last menstrual period (LMP): 8:38
Menstruation or period is regular discharge of blood and mucosal tissue from the uterus through the vagina: 9:02
Mucous membrane or mucosa is a membrane that lines various cavities in the body and covers internal organs: 9:28
Uterus or womb is where the fetus develops during gestation: 9:37
Gestation is period of development during the carrying of the embryo / fetus: 10:01
Hormone is a signaling molecule that regulates physiology and behavior: 10:23
Sex organ or reproductive organ is any part involved in sexual reproduction: 10:50
Primary sex organs are testis in the male and ovary in the female: 11:04
Secondary sex organs include external (genitals) and internal sex organs (genitals): 11:10
Uterus and uterine tubes diagram: 11:22
Menstrual cycle diagram. Period occurs every 21 to 35 days : 11:37
- Follicular phase: Eggs mature inside small follicles: 11:52
- Ovulation: Egg is released from biggest follicle: 12:05
- Follicle is a small cellular cavity in which other structures grows or other material is contained: 12:32
- Luteal phase: Endometrium (lining of uterus) is thick to support a pregnancy: 12:59
- Menstruation: "Period" when the endometrium is shed over 3-7 days if there is no pregnancy: 13:25