Histology

Histology Intro

Histology

Histology is the microscopic structure or anatomy of tissue. By understanding the normal order of cells in tissue, this helps with recognizing abnormal structure of cells in tissue. This can be very important for diagnosis of diseases, such as cancer.


Histology Slide Preparation

Learn about how the specimens are prepped by watching Dr. Goldsmith in the video below! Following this are some examples of histology images from different body systems.


Now lets look at some slides!


Blood Vessels

Circulatory System- Blood Vessels

Blood (Wể) is moved throughout the body by the circulatory system. It is pumped by the heart (Châde) and uses arteries and veins like highways to get to the tissues and cells. Red blood cells transport oxygen throughout the body and remove carbon dioxide. Arteries transport blood from the heart to the tissue, while veins transport blood in the opposite direction from the tissues to the heart. Therefore, arteries and veins are named according to which direction they move blood, not based on the oxygenation of the blood. Arteries tend to have a lot more smooth muscle surrounding them. This is because they are required to handle high pressured blood that is being pumped from the heart. Since the blood returning to the heart is less pressurized, veins have much less smooth muscle and therefore are much thinner walled compared to arteries.


Skeletal Muscle

Muscles- Skeletal Muscle

There are three different types of muscles (Ka) in the body. There is skeletal muscle, which make up the muscles on your skeleton, such as your triceps or hamstrings. There is smooth muscle, which makes up the involuntary muscle of many organs, such as your bladder. Finally, there is cardiac muscle which makes up the muscles of your heart. Skeletal muscle fibers are multinucleated, meaning they have many nuclei, and are made up of myofibrils. Myofibrils are the smaller units of long fibers that run in the same direction to form muscle. Myofibrils are wrapped with connective tissue called endomysium, to form muscle fibers. Think of the connective tissue as wrapping a bunch of spaghetti in plastic wrap. These bunches of muscle fibers are then wrapped in connective tissue called perimysium. Finally, an individual skeletal muscle is made up of numerous skeletal muscle fibers that have been bunched together and wrapped with connective tissue called epimysium. Now all these fibers work together to create movement, by shortening in length and pulling on bones.


Lung

Respiratory System- Lung Alveoli

Respiration is the movement of oxygen from the outside environment into cells, and the movement of carbon dioxide out of cells and into an outside environment. Most animals use their lungs (Charhu) and circulatory system to get oxygen from the outside environment into their cells. Oxygen gets into your blood (Wể) through a process called diffusion. Diffusion is the passage of molecules from an area of high concentration to an area of low concentration. This can be visualized by dropping food coloring in water; the dye will move from the concentrated droplet and slowly diffuse into the water. To accomplish this, your lungs need to bring air into really close contact with your blood. To do this, your lungs have alveoli (small pockets of air) that clump together in a way that makes them look like a cluster of grapes. Alveoli are made up of a very thin wall that is only one cell layer thick and contains tiny blood capillaries: an optimal environment for gas exchange.


Skin

Integument System- Skin

The integument system is the external protective covering of the body, this includes structures like skin (Ha), hair (Nâdu), nails (Sagể) and sweat glands. Skin is comprised of the epidermis and the dermis. Epidermis is what you see when you look at your skin and is composed of a tough, thick layer of epithelial cells. The dermis is underneath the epidermis and is comprised of loose connective tissue including blood vessels and nerves. Hair follicles and sweat glands originate deep in the dermis and connect to the overlying epidermis. Glands, such as sweat glands, will usually empty into an adjacent hair follicle.


Duodenum

Small Intestine- Duodenum

The small intestine (Sube) is the location of a lot of food (wonâpche) digestion and absorption. There are three parts to the small intestine: the duodenum, jejunum, and ileum. The duodenum is the first part of the small intestine. Once food passes through the stomach (Tethi), the digesta (chewed up food) enters the duodenum and is mixed with pancreatic juices and bile from the gall bladder and liver. Since there are digestive juices in this area it is important to protect the duodenal tissue. One way that the cells are protected is through mucous secretion. The cells that secrete mucous are called goblet cells. Due to the amount of absorption occurring in this area, the small intestine has many crypts and villi to increase its surface area. Villi are finger like projections, while crypts are small pits in the tissue. The individual cells lining the surface, called enterocytes, even have their own tiny villi called microvilli, that again help to increase surface area for nutrient absorption. Think of this as similar to trying to soak up a large water spill with a paper towel versus a big cotton beach towel, with lots of little fibers like villi.


Bone

Hard Connective Tissue- Bone

Did you know that bone is classified as hard connective tissue? This is a picture of the growth plate of a bone (Huhu) (also known as an epiphyseal disc). In this section, you can see something called endochondral bone formation. This is how bones, like the femur in your leg, get longer as you grow. Endochondral bone formation is where cartilage is formed first, and then later ossification occurs to turn it into bone. It is important to remember that the cartilage does not become bone itself, but is used as a template to create bone. Osteoblasts are the cells in this area that produce the bone matrix. Once osteoblasts produce the bone matrix, they mature and flatten to become osteocytes. These live in a space called a lacuna. Canaliculi are tiny channels within the bone matrix that contain things like blood vessels that allow for nutrients and oxygen to get to these cells, as well as for waste material to be removed.


Retina

Special Senses- Eye

Eyes (îsta) are a very interesting and complex form of tissue that allow for sight. There are many structures in the eye (îsta), but the structure that changes light to an electrical signal that can be used by the brain to create an image is called the retina. The retina is composed of numerous layers. The layer that changes light into electrical signals that can be used by the brain is called the photoreceptive layer. In this layer, there are special cells called rods and cones that are sensitive to light. Rods are important for vision in a low light environment, such as at nighttime, while cones are responsible for vision in a high light environment, such as during the day, and allow you to perceive colour. Since portions of the retina are made of neuronal tissue, this tissue does not regenerate when damaged. Because of this, vision is not likely to return once it is damaged and lost. Isn’t it interesting that light needs to pass through numerous layers of cells before it even hits this photoreceptive layer?


Kidney

Renal System- Kidney

The kidney (Azûkta) is the organ in the body that filters the blood and makes urine. The kidneys play a large role in water (Mînî), salt (Tasuza), and waste retention/removal in the body. The smallest working structure of the kidney is called the nephron. A nephron is a miniature tube-like structure that uses mechanisms such as diffusion to filter the blood (Wể) and collect waste that will be excreted as urine. There are different portions of a nephron that play many different roles in the removal of salt, water, and waste. The first point where capillaries (tiny blood vessels) encounter the nephron is called the glomerulus. The glomerulus looks kind of like a ball of yarn, and this is where most of the waste from the blood is filtered out. This waste is filtered out into an area called the Bowman’s capsule of the nephron. The Bowman’s capsule is like the entrance to the tube structure that is the nephron. 


Spinal Cord

Nervous System- Spinal Cord

In this image of a section of spinal cord (Châkahu îmehen kâ ze) you can see the presence of white matter (pale blue) and grey matter (dark blue). Before staining, white matter is white in colour because this is the location of the axons of the cells. An axon is like a pipe that is used by a neuron or nerve to move a message or nerve impulse from one end to another. The axons are white in colour as they are surrounded by oligodendrocytes (within the brain and spine) or Schwann cells (within the peripheral nervous system). Oligodendrocytes/Schwann cells increase the speed at which the message can be transmitted and are white in colour due to their high fat content. The grey matter is where the cell bodies are located. It is split into the ventral and dorsal horns, named this due to their horn-like shape. The dorsal horn contains the cell bodies of sensory neurons which relay information about touch and vibration, while the ventral horn contains cell bodies of motor neurons which control movements of your muscles. The spinal cord is surrounded by a protective outer sheath called the dura mater.