Lab Two Flashcards
Where are tonsils found?
We have three main pairs of tonsils found in various locations throughout the pharynx:
- Pharyngeal tonsils (adenoids): located in the posterior wall of the nasopharynx
- Palatine tonsils: located on either side at the back of the oral cavity (mouth) at the junction of the mouth and throat
- Lingual tonsils: not visible but located under the mucosa in the base of the tongue
What structures are found in the splenic hilus?
In the splenic hilus we can find the splenic artery and vein, as well as the lymphatics which drain the spleen.
Identify the difference between the diaphragmatic and visceral (gastric and renal) surfaces of the spleen.
The diaphragmatic surface of the spleen rests flush with the diaphragm, whereas the visceral surface is divided into the renal and gastric areas. The renal area is rather smooth and concave, whereas the gastric area is convoluted to reflect the rugae of the stomach.
Where are Peyer’s patches found?
Peyer’s patches can be found in the lamina propria and submucosa of the ileum (part of the small intestine). They are components of mucosa-associated lymphatic tissue (MALT).
Describe the anatomical relationships of the adult human spleen.
The spleen is located on the left side of the abdominal cavity just below the diaphragm. It lies along the lateral border of the stomach. The spleen is snuggled between the stomach and left kidney (anteriorly and medially respectively), diaphragm (superiorly), and the rib cage (laterally).
How do lymphatic pathways begin?
Lymphatic pathways begin as lymphatic capillaries. Endothelial cells are often considered specialized epithelial cells which line blood vessels. Lymphatic capillaries are most comparable to sinusoidal capillaries.
What kind of walls are those of lymphatic vessels similar to?
Lymphatic vessel walls closely resemble those of veins and often contain valves to prevent backflow of lymph.
Describe the new theory as to how T lymphocytes enter into the circulatory system.
T lymphocytes divide and develop in the thymic cortex; however, it is hypothesized that they move towards the corticomedullary junction where blood vessels are found.
Describe the structural framework of the thymus.
The structural framework of the thymus is specialized epithelial cells called thymocytes, unlike that of reticular fibres in other lymphoid organs. These epithelial cells make up the blood-thymus barrier, which prevent the contact of antigens found in the blood and developing immature lymphocytes found in the thymic cortex.
The thoracic duct lies adjacent to which major vessel?
The thoracic duct lies adjacent to the thoracic aorta. On the right side of the thoracic duct, you may find the azygos vein. The left internal jugular vein is adjacent to the duct as it makes its connection with the left subclavian vein.
Describe the subcapsular sinus.
The subcapsular sinus is the space found directly underneath the lymphatic capsule. This sinus is composed of reticular fibres, macrophages, and dendritic cells (i.e. it is made of diffuse lymphatic tissue). Once lymph enters the nodes through the afferent vessels, it will first pass through this sinus to begin the process of filtration.
What is the germinal center?
The germinal center is the palest region of the lymphatic nodule. This area mainly consists of actively dividing B lymphocytes.
Describe the histological organization of the thymus.
The thymus is a bi-lobed organ. The thymus is surrounded by a capsule composed of connective tissue. Additionally, it contains septa (trabeculae) which divide it into lobules. Within each lobule, it is divided into a subcapsular, cortical, and medullary region. Oddly, the medulla contains a diffuse, paler core. This is because the cortex contains stem cells that are developing and maturing into T lymphocytes (stain darker). The medulla contains some of the mature T cells, epithelial cells, and Hassall’s corpuscles.
What is the cisterna chyli and where is it found?
The cisterna chyli is where the thoracic duct begins below the diaphragm at the level of the second lumbar vertebrae as an expanded sac-like chamber.
Describe the anatomical relationships of the adult human thymus.
The adult human thymus is located in the lower portion of the neck and extends down the upper portion of the mediastinum, partially covering the superior portion of the heart. It lies in front of the trachea and great vessels of the heart, behind the sternum, and on each lobule of the thymus are the lungs. The organ is pinkish-grey.
What is the function of the thymus?
The function of the thymus is for the development and maturation of T lymphocytes.
Which lymphatic trunk drains the abdominal viscera?
The intestinal trunk.
What are Hassall’s corpuscles and where are they found?
Hassall’s corpuscles are epithelial cells (thymocytes) which cluster together in concentric layers, forming these distinctive structures. They can be found in the medulla of the thymus.
What kind of epithelium is seen near Peyer’s patches?
The epithelium found near Peyer’s patches is made of simple columnar due to its location within the small intestine (ileum).
Describe the types of immune cells found in lymph nodes.
In the cortex, the lymphatic nodules contain B lymphocytes. The subcortical portion is occupied by T lymphocytes. The medullary cords are mainly composed of B lymphocytes and plasma cells.
What kind of epithelium is found near tonsils?
The epithelium found near tonsils is stratified squamous. This is due to its location in the oral region, meaning it is exposed to a lot of wear and tear.
What is the difference between efferent and afferent lymphatic vessels?
Afferent lymphatic vessels bring lymph to the lymph node from peripheral tissue, whereas efferent lymphatic vessels take lymph away from lymph nodes.
The thoracic duct drains into which major vessel?
The thoracic duct drains into the left subclavian vein. This vein can be found near the junction of the left internal jugular vein.
The thoracic duct collects lymph from what areas of the body?
The thoracic duct collects lymph from the left-hand side of the body above the diaphragm, as well as both sides of the body below the diaphragm.
What kind of blood cells are found in the red and white pulp of the spleen?
The red pulp consists of red blood cells and lymphocytes. The white pulp contains mainly B lymphocytes.
Which lymph nodes drain the knee and lower limb regions?
The popliteal nodes filter lymph arriving from the leg. The inguinal nodes located in the groin region filter lymph arriving at the trunk from the lower limbs.
Define the cortex and medulla of the lymph nodes.
The cortex of the lymph node is considered the outer portion. The lymphatic nodules are located in the cortex. Around each nodule in the cortex and each cord in the medullar are the lymphatic sinuses. The innermost portion of the lymph node is considered the medulla. There you will find elongated, irregular masses of lymphatic tissue and cells called medullary cords.
Describe the histology of tonsils.
Tonsils are part of the mucosa of their respective region of the digestive tract. They contain lymphatic nodules as well as crypts. These crypts greatly increase the contact surface between environmental influences and lymphatic tissue.
Describe the histological organization of the spleen.
The spleen is surrounded by a capsule made of collagen and elastic fibres. The cellular and tissue components are called pulp: white and red respectively. The white pulp resembles lymphatic nodules and tends to stain darker. They cluster around arteries. On the other hand, red pulp is made of diffuse lymphatic tissue. On an important note, the trabeculae of the spleen do not divide it into lobes or lobules.
What is the hilus of the lymph node?
The hilus is the concave surface of the node. This is where efferent vessels, blood vessels, and nerves are attached.
Which lymphatic trunks drain the head and neck?
The jugular trunks (right and left) drain the head and neck.
