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Nondisjunction

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

Testes: Histology

Testes: Histology

A tough, fibrous membrane, the tunica albuginea, covers the testes, extending inward to form fibrous partitions or septa, dividing them into internal compartments called lobules. Each lobule has 1 to 3 tightly coiled seminiferous tubules where sperm production occurs. These tubules merge into a tubular network at the back of the testis, known as the rete testis. It connects to 15 to 20 efferent ductules, leading to the epididymis.
The spermatogenic cells, responsible for producing sperm, are...

Testes: Gross Anatomy

Testes: Gross Anatomy

The testes, also known as testicles, are the male gonads. They are housed within the scrotum, a sac-like structure located beneath the penis. The scrotum's primary role is to regulate the temperature of the testes, which is crucial for sperm production.
Each testis is surrounded by the tunica albuginea, a dense connective tissue layer that provides structural support and protection. This layer is covered by an outer serous membrane called the tunica vaginalis, which helps reduce friction...

Meiosis I

Meiosis I

Meiosis is a carefully orchestrated set of cell divisions, the goal of which—in humans—is to produce haploid sperm or eggs, each containing half the number of chromosomes present in somatic cells elsewhere in the body. Meiosis I is the first such division, and involves several key steps, among them: condensation of replicated chromosomes in diploid cells; the pairing of homologous chromosomes and their exchange of information; and finally, the separation of homologous chromosomes by a...

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Related Experiment Video

Updated: May 14, 2026

Microsurgical Obstruction of Testes Fusion in Spodoptera litura

Microsurgical Obstruction of Testes Fusion in Spodoptera litura

Published on: July 16, 2021

Polyorchidism: a torted right-sided supernumerary testis.

Mandela Thyoka¹, Anupam Lall, Alok Godse

¹Department of Paediatric Surgery, UCL Institute of Child Health, London, UK. m.thyoka@ucl.ac.uk

BMJ Case Reports

|February 19, 2013

Summary

This summary is machine-generated.

Polyorchidism, a rare congenital condition, involves having more than two testes. This case highlights a unique instance of right-sided triorchidism discovered during surgery for an inguinal hernia in a teenage boy.

Related Experiment Videos

Last Updated: May 14, 2026

Microsurgical Obstruction of Testes Fusion in Spodoptera litura

Microsurgical Obstruction of Testes Fusion in Spodoptera litura

Published on: July 16, 2021

Area of Science:

Urology
Pediatric Surgery
Congenital Anomalies

Background:

Polyorchidism is a rare congenital anomaly characterized by the presence of more than two testes.
Triorchidism, the most common variant, typically involves a supernumerary testis on the left side.
Often diagnosed incidentally during procedures for associated conditions like undescended testes or hernias.

Observation:

A 15-year-old boy presented with an irreducible right inguinal hernia.
Surgical exploration revealed a right-sided triorchidism, a rare presentation.
The supernumerary testis was located on the right side, deviating from the common left-sided occurrence.

Findings:

Histological confirmation of three testes in the affected individual.
The supernumerary testis was identified during the surgical management of a right inguinal hernia.
This case represents a rare instance of right-sided triorchidism.

Implications:

Highlights the importance of thorough intraoperative examination during hernia repair in pediatric patients.
Contributes to the understanding of rare congenital anomalies and their varied presentations.
Underscores the potential for incidental diagnosis of polyorchidism in surgical settings.