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Basic histological staining methods (preview) - Human Histology | Kenhub DrPhil 83 Views • 2 years ago

In order to be able to look at tissues under a microscope, we need to first stain them with the right technique. Learn the main staining techniques used in histology today on our full video: https://khub.me/aux9w

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As you probably know, histology is the study of the microscopic anatomy of cells and tissues. So we use staining methods to visualize and distinguish the different parts of cells and tissues since cells and their structures are usually transparent or colorless. The types of dyes used to color cells and their components can either be specific to particular structures, chemical groups or even molecules, and it can also be non-specific in which case most of the cell is stained in the same way.

When staining tissue samples, dyes that are used are either acidic or basic or a combination of the two. And why is that, you might be asking. Well, cellular structures such as nucleic acids or proteins have charged groups which are known as phosphate groups or carboxyl groups, just to name a couple. The dyes used in histology are colored organic compounds which also have a charge. Acidic dyes carry a negative charge and so they bind to positively-charged cell structures.

In the full version of this tutorial, we will cover some of the most common types of dyes used in histological staining of cells and their structures:
- basic dyes vs acidic dyes vs neutral dyes;
- hematoxylin and eosin;
- PAS - staining;
- Golgi method;
- Toluidine blue;
- Masson's trichrome;
- Osmium tetroxide;

To master this topic, click on the link and carry on watching the full video (available to Premium members): https://khub.me/aux9w !

Want to test your knowledge on the different types of cells and tissues? Take this quiz: https://khub.me/3g19f

Read more on how to interpret different histological sections on this complete article which goes through the different stains used in histology https://khub.me/saimh

For more engaging video tutorials, interactive quizzes, articles and an atlas of Human anatomy and histology, go to https://khub.me/pkvz2

Spontaneous Breech Delivery Childbirth Mohamed 22,019 Views • 2 years ago

A breech birth is the birth of a baby from a breech presentation. In the breech presentation the baby enters the birth canal with the buttocks or feet first as opposed to the normal head first presentation.

There are either three or four main categories of breech births, depending upon the source:

* Frank breech - the baby's bottom comes first, and his or her legs are flexed at the hip and extended at the knees (with feet near the ears). 65-70% of breech babies are in the frank breech position.

* Complete breech - the baby's hips and knees are flexed so that the baby is sitting crosslegged, with feet beside the bottom.

* Footling breech - one or both feet come first, with the bottom at a higher position. This is rare at term but relatively common with premature fetuses.

* Kneeling breech - the baby is in a kneeling position, with one or both legs extended at the hips and flexed at the knees. This is extremely rare, and is excluded from many classifications.

As in labour with a baby in a normal head-down position, uterine contractions typically occur at regular intervals and gradually cause the cervix to become thinner and to open. In the more common breech presentations, the baby’s bottom (rather than feet or knees) is what is first to descend through the maternal pelvis and emerge from the vagina.

At the beginning of labour, the baby is generally in an oblique position, facing either the right or left side of the mother's back. As the baby's bottom is the same size in the term baby as the baby's head. Descent is thus as for the presenting fetal head and delay in descent is a cardinal sign of possible problems with the delivery of the head.

In order to begin the birth, internal rotation needs to occur. This happens when the mother's pelvic floor muscles cause the baby to turn so that it can be born with one hip directly in front of the other. At this point the baby is facing one of the mother's inner thighs. Then, the shoulders follow the same path as the hips did. At this time the baby usually turns to face the mother's back. Next occurs external rotation, which is when the shoulders emerge as the baby’s head enters the maternal pelvis. The combination of maternal muscle tone and uterine contractions cause the baby’s head to flex, chin to chest. Then the back of the baby's head emerges and finally the face.

Due to the increased pressure during labour and birth, it is normal for the baby's leading hip to be bruised and genitalia to be swollen. Babies who assumed the frank breech position in utero may continue to hold their legs in this position for some days after birth.

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