Human sperm structure

Summary

The human sperm is a complex motile cell composed of a head, neck, middle piece, and tail. The head contains 23 chromosomes within a nucleus, covered by an acrosome crucial for fertilization. Two centrioles within the sperm play a role in forming the mitotic spindle post-fertilization. The tail, divided into the principal and end pieces, lacks mitochondria and is supported by fibrous sheaths, with the axoneme at its core providing motility. This detailed structure is essential for sperm function and fertilization.

Takeaways

• 🌟 The human sperm is a motile cell composed of four main parts: head, neck, middle piece, and tail.
• 🔬 The sperm head is roughly 5 micrometers long and contains the nucleus with 23 chromosomes, which is crucial for fertilization.
• 🧬 The anterior two-thirds of the nucleus is covered by the acrosome, which contains enzymes that help in penetrating the oocyte.
• 🔧 The middle piece of the sperm contains two centrioles, which play a vital role in forming the mitotic spindles after fertilization.
• 🏋️‍♂️ The tail is composed of a principal piece and an end piece, with the principal piece lacking certain microtubules and instead having fibrous sheaths for support.
• 🏃‍♂️ The axoneme, found in the tail, has a '9+2' structural pattern, which is essential for sperm motility.
• 🔋 The middle piece is surrounded by tightly packed mitochondria, which provide the energy necessary for sperm movement.
• 🛡️ The connecting piece connects the head to the tail and is crucial for maintaining the integrity of the sperm structure.
• 🚫 Decapitated sperm, where the connecting piece is displaced, cannot swim and therefore cannot reach the oocyte.
• 🏁 The end piece of the tail is covered only by the plasma membrane, lacking the outer dense fibers and fibrous sheaths present in the principal piece.

Q & A

What are the four main parts of a human sperm?

The four main parts of a human sperm are the head, neck, middle piece, and tail.

What does the sperm head resemble in shape?

The sperm head resembles an egg with a narrow cranial part and a wider caudal part.

How long is the sperm head and what occupies most of its space?

The sperm head is about 5 micrometers in length, and most of its space is occupied by the nucleus.

How many chromosomes does the nucleus contain and what is their role?

The nucleus contains 23 chromosomes, which are the genetic material from the father required for fertilization.

What is the function of the acrosome and what does it contain?

The acrosome is a cap covering the anterior two-thirds of the nucleus and contains proteolytic enzymes known as lysosomal enzymes, which help in digesting structures surrounding the oocyte to enable sperm penetration.

What are the two centrioles associated with the nucleus and where are they located?

The two centrioles are the proximal centriole, located in the implantation fossa, and the distal centriole, located slightly distal at the neck region.

What is the significance of the proximal centriole after fertilization?

The proximal centriole forms the mitotic spindles required for chromosome separation after fertilization.

What is the function of the connecting piece and how is it connected to the head and tail of the sperm?

The connecting piece connects the head to the tail of the sperm. It is surrounded and connected by a banded structure, and displacement of this piece from the implantation fossa can result in the head separating from the tail.

What is the 9 plus 2 structural pattern and where is it found in the sperm?

The 9 plus 2 structural pattern refers to the axoneme, which has two central microtubules surrounded by nine peripheral doublet microtubules. This pattern is found in the tail of the sperm.

How are the mitochondria arranged in the middle piece of the sperm and what is their role?

The mitochondria in the middle piece are arranged in a tightly packed, helical pattern around the axoneme. They provide the energy required for sperm motility.

What are the two parts of the tail and how is the axoneme covered in each part?

The tail consists of the principal piece and the end piece. In the principal piece, the axoneme is covered by two fibrous supports, the outer dense fibers (ODF) and the fibrous sheaths. In the end piece, the axoneme is directly covered by the plasma membrane without ODF and fibrous sheets.