oocyte - Meiosis I

A mature oocyte (egg cell) does not complete meiosis right after ovulation. Here’s the timeline in simple steps:

1. Before birth – Primary oocytes begin meiosis I but stop in prophase I (they stay paused for years).

2. At puberty – Each menstrual cycle, under FSH and LH signals, some primary oocytes continue meiosis I.

   • One usually completes meiosis I just before ovulation → producing a secondary oocyte + a small first polar body.

3. At ovulation – The secondary oocyte starts meiosis II but stops again in metaphase II.

4. Completion of meiosis II – This only happens after fertilization by a sperm. Then, the oocyte quickly finishes meiosis II, producing a mature ovum and a second polar body.

👉 So to answer clearly:

• A mature oocyte completes meiosis I just before ovulation, not after.

• It only completes meiosis II after fertilization.

Progesterone Hormone

 Decreasing level of progesterone lead to sloughing or shedding of the endometrium lining.

 Decreasing level of progesterone lead to sloughing or shedding of the endometrium lining 

Decreasing Level of Progesterone lead to sloughing or shedding of the endometrium lining

Decreasing level of progesterone level lead to sloughing or shedding of the endometrium lining 

Gonadotrophic hormone released by the

 Gonadotrophic hormone released by the 

Anterior pituitary gland

Gonadotrophic hormones are released by the anterior pituitary gland in response to gonadotropin-releasing hormone (GnRH), which is produced by the hypothalamus. 

These hormones, including follicle-stimulating hormone (FSH) and luteinizing hormone (LH), play crucial roles in regulating reproductive functions in both males and females. 

Meiosis

During meiosis, homologous pairs of chromosomes can exchange pieces of DNA after they synapse. 

https://slidetodoc.com/ch-10-sexual-reproduction-genetics-10-1-meiosis/

1. Synapsis

In prophase I of meiosis, homologous chromosomes

 (one from mom and one from dad) line up tightly side by side.

This close pairing is called synapsis, and the structure formed is called a tetrad (4 chromatids together).

2. Crossing Over

At points called chiasmata, the non-sister chromatids exchange segments of DNA.

This swaps genes between maternal and paternal chromosomes.

3. Result

After crossing over, the chromosomes are genetically recombined.

This increases genetic diversity, which is why siblings look different even with the same parents.

https://slidetodoc.com/ch-10-sexual-reproduction-genetics-10-1-meiosis/

👉 In short: During meiosis, after homologous chromosomes synapse, they can exchange DNA through crossing over, creating new gene combinations.

Smallest to Largest muscle

1.  Myofilament 
2. sarcomere
3. Myofibril 
4. muscle fiber 
5. fascicle 
6. whole muscle   

MSM -MFW

1. myofilament 
2. sarcomere
3. myofibril
4. muscle fiber 
5. fascicle 
6. whole muscle 

MSMMFW

1. myofilament
2. sarcomere
3. myofibril
4. muscle fiber 
5. fascicle 
6. whole muscle 

myofibril

 Tightly packed filament bundles found within skeletal muscle fibers called myofibril 

Tightly packed filaments bundles found within skeletal muscle fibers called myofibril. 

Tightly packed filaments bundles found within skeletal muscle fibers called myofibril

Tightly packed filaments bundles found within skeletal muscle fibers called myofibril

Tightly packed filaments bundles found within skeletal muscle fibers called myofibril

Fascicle

 bundle of muscle fibers is called fascicle 

Bundle of muscle fibers is called fascicle

 Bundle of muscle fibers is called fascicle 

Bundle of muscle fibers is called fascicle 

Bundle of muscle fibers is called fascicle 

Myofilaments

 Myofilament - Filament of myofibrils constructed from proteins , principally myosin or actin 

Myofilament -Filament of myofibrils constructed from protein principally myosin and actin filaments 

Myofilament filament of myofibrils constructed from protein principally from actin and myosin  

Myofilaments -Filament of myofibrils constructed from protein principally from actin and myosin

Golgi Appratus

Package of protein

 

Endoplasmic reticulum

 Both type of cell 

carries substances, like protein to various part of the cell  .

• Protein synthesis ,
•  lipid metabolism, 
• cellular signaling

Ribosome

 Ribosome - Protein synthesis

Cytoplasmic organelles at which proteins are synthesized.

Ribosomes translate messenger RNA (mRNA) into polypeptide chains, linking amino acids in the order specified by the mRNA codons, which is essential for cellular function and growth

 Cytoplasmic organelles at which proteins are synthesized. 

Lysosome

 An organelle that contains digestive enzyme

An organelle that contains digestive enzyme 

 A lysosome is a small, round organelle found mainly in animal cells. It works like the cell’s recycling and cleanup center.

Mitochondria

 Power house of cell production - 

Main function: They produce energy in the form of ATP (adenosine triphosphate) through a process called cellular respiration.

Mitochondria - Powerhouse of cell production -

mitochondria - Powerhouse of cell production -

Nuclear Membrane

 Nuclear Membrane controls what goes in and out of nucleus 

Nuclear membrane controls what goes in and out of nucleus 

Nuclear membrane controls what goes in and out of nucleus 

Nuclear membrane controls what goes in and out of nucleus 

Nuclear membrane control what goes in and out of nucleus 

Cell Membrane

Thin covering that holds the cell together.

 It controls what enter and leave the cells.

Cell membrane - thin covering that hold the cells together. It controls what enter and leave the cell 

Prokaryotes

  A unicellular organism lacks a nucleus and membrane bound organelles

Eukaryotes

 A cell that contains nucleus and membrane bound organelles

Vaculoe

 A cell contains a nucleus and membrane bound organelles 

A vacuole is a membrane-bound sac found inside cells.

Its main job is to store materials. 

What it stores depends on the type of cell:

In plant cells: vacuoles are usually very large (called central vacuoles). They store water, nutrients, and waste products. They also help keep the plant rigid by maintaining turgor pressure (water pressure inside the cell).

In animal cells: vacuoles are smaller and more numerous. They help store nutrients, waste, or other small molecules, and sometimes assist in breaking down materials.

In unicellular organisms (like amoebas): some vacuoles pump out extra water (contractile vacuoles), while others help digest food (food vacuoles).

Practice : 

A cell contains a nucleus and membrane bound organelle 

Nucleolus

 small dense region within most nuclei in which the assembly of protein begins.

small dense region within most nuclei in which the assembly of protein begins. 

small dense region within most nuclei in which the assembly of protein begins

small dense region within most nuclei in which the assembly of protein begins 

a small dense region within most nuclei in which the assembly of protein begin

 a small dense region within most nuclei in which the assembly protein begin

Cranial Nerves

 

heart Anatomy

 

Chloroplast

 Chloroplast- A green plant cells a plastid that contains chlorophyll and which photosynthesis take place.

A green  plant cell a plastid that contain chlorophyll and which photosynthesis take place 

A green plant cell a plastid that contains chlorophyll and which photosynthesis take place.

A green plants cell plastid that contains chlorophyll and which photosynthesis take place.

A green plant cell that   plastid contains chlorophyll which photosynthesis take place.