Structure Of Sperm: Definition, Structure, Function

Sperm is the male reproductive gamete, which takes part in the anisogamous mode of sexual reproduction (in which there is a larger, female reproductive cell and a smaller, male one). They generally have a head, a middle piece, and a tail. They are motile and can travel from the reproductive tract to the fallopian tube for fertilisation.

This Story also Contains

1. What is Sperm?
2. Structure of Sperm
3. Spermatogenesis
4. Abnormalities in the Structure of Sperm
5. MCQs on the Structure of Sperm
6. Recommended Video On 'Structure of Sperm'

Sperms are produced during spermatogenesis in the seminiferous tubules of the testes. The process starts with spermatogonia and results in the formation of sperm cell precursors, which eventually mature into spermatocytes. The spermatocytes then undergo various stages of meiosis and generate spermatids. The spermatids then mature into spermatozoa, having a head, a middle piece, and a tail. The structure of sperm is an important topic in the biology subject.

What is Sperm?

Sperm, or spermatozoa, are the male gametes that fertilise the female oocyte to form a zygote. In summary, a sperm cell contains half of the genetic material for the formation of a new individual, so its contribution to sexual reproduction is very important.

Structure of Sperm

• A typical sperm cell is designed to carry genetic material to the egg efficiently.

• It is divided into the head, the midpiece, and the tail.

• Head: It contains the very front part of the nucleus, which contains the genetic material. The latter is, in turn, covered by the acrosome.

• Midpiece: This region of the sperm is filled with mitochondria, which supply the energy needed for movement.

• Tail: A long, whip-like structure that propels the sperm forward.

Sperm Head

• The sperm head is responsible for penetrating the egg and providing genetic material.

• It is formed with an acrosome that provides enzymes to penetrate the outer layers of the egg.

• The nucleus within the sperm contains the DNA that later fuses with the egg DNA at fertilisation.

Midpiece of Sperm

• The midpiece of the sperm is specialised to provide energy for movement.

• Mitochondria help to generate ATP (adenosine triphosphate), the energy currency of the cell. The energy helps to propel the sperm from the female reproductive tract to the site of fertilisation in the fallopian tube.

Tail of Sperm

• The tail makes sperm motile and thus helps it to swim towards the egg.

• Generates a whiplike motion.

• Aids in travel through the cervical mucus.

Spermatogenesis

Spermatogenesis is the process by which sperm are generated within the testes. It involves several stages, including mitosis, meiosis, and sperm maturation, regulated by hormones like FSH and testosterone.

Overview of Process

• Starts at the age of puberty and continues throughout life.

• Takes place in the seminiferous tubules of the testes.

Stages of Spermatogenesis

• Spermatogonia: Division of stem cells leads to primary spermatocytes.

• Primary Spermatocytes: Meiosis I results in secondary spermatocytes.

• Secondary Spermatocytes: Meiosis II leads to the formation of spermatids.

• Spermatids: Mature to become spermatozoa.

Abnormalities in the Structure of Sperm

Structural abnormalities in sperm may involve defects in the head, midpiece, or tail. These abnormalities can affect sperm motility, fertilisation capability, and may lead to infertility in severe cases.

MCQs on the Structure of Sperm

Q1. Tail of sperm cell in human beings

Option 1: Contain mitochondria and help in cell division

Option 2: Contain acrosome and help in movement

Option 3: Contain endoplasmic reticulum

Option 4: Facilitates sperm motility essential for fertilization

Correct answer: (4) Facilitates sperm motility essential for fertilization

Explanation:

Structure of Sperm -

• It is a microscopic structure composed of a head, neck, a middle piece and a tail.

Tail:

• It is several times longer than the head.

• It is made up of an axial filament surrounded by a thin layer of cytoplasm.

• The end-piece is made up of naked axial filament.

• It provides motility to the sperm.

Hence, the correct answer is option 4) Facilitates sperm motility essential for fertilization

Q2. The mobility of a mature sperm is controlled by the mitochondria located in the

Option 1: Head

Option 2: Middle piece

Option 3: Tail

Option 4: All of them

Correct answer: (2) the middle piece

Explanation:

The middle piece of a sperm cell contains numerous mitochondria, which are responsible for producing the energy required for the movement of the tail (flagellum). This energy is essential for the sperm's motility, enabling it to swim toward the egg during fertilization. The mitochondria in the middle piece generate ATP through cellular respiration, fueling the sperm's movement and facilitating its journey.

Hence, the correct answer is option 2) the middle piece

Q3. Match between the following representing parts of the sperm and their functions and choose the correct option.

Option 1: A-ii, B-iv, C-i, D-iii

Option 2: A-iv, B-iii, C-i, D-ii

Option 3: A-iv, B-i, C-ii, D-iii

Option 4: A-ii, B-i, C-iii, D-iv

Correct answer: (2) (A) – (iv), (B) – (iii), (C) – (i), (D) – (ii)

Explanation:

The sperm cell is specialized for reproduction, with each part serving a critical function. The nucleus in the head contains the genetic material, while the acrosome releases enzymes to dissolve the zona pellucida of the egg for fertilization. The middle piece is packed with mitochondria to generate energy (ATP) for movement, and the tail or flagellum propels the sperm, enabling it to swim towards and fertilize the egg efficiently.

Hence, the correct answer is option (2) (A) – (iv), (B) – (iii), (C) – (i), (D) – (ii)

Recommended Video On 'Structure of Sperm'