Connective Tissue Theoretical Test Locomotor System 1 PDF

Connective tissue Theoretical test Locomotor system Theoretical test Part 1: Embryonic and Adult Connective Tissue 1. Basic composition of connective tissue (CT) Connective tissue - Connective tissue lies under the epithelia of all tissues and organs. The connective tissue is always und...

Connective tissue Theoretical test Locomotor system Theoretical test Part 1: Embryonic and Adult Connective Tissue 1. Basic composition of connective tissue (CT) Connective tissue - Connective tissue lies under the epithelia of all tissues and organs. The connective tissue is always under the epithelial because the epithelial doesn’t have any blood vessels but the connective tissue does. Because epithelial doesn't have any blood vessels it cannot get any nutritions, not get oxygenized, not get rid of waste products, and cannot have a metabolism. By diffusion the epithelial tissue can get all the nutrients and the oxygen that's needed from the connective tissue. Nutrients and oxygen: From capillaries to the epithelial. Waste products: from epithelial to the capillaries. - It provides structural and metabolic support of the surrounding tissue, as it contains the blood vessels, and can also contain adipocytes. - The extracellular matrix also regulates cell proliferation, migration and differentiation - Cartilages are a type of connective tissue, found at the end of a bone, which are attached with joints. By having cartilages we are able to move without anything hurting - Bones are also a type of connective tissue - Blood does also classify as a connective tissue even if it's liquid, many different functions. RBC carries oxygen WBC are our immune system Connective tissue has two main parts: Cells and extracellular matrix (ECM) Extracellular matrix (ECM) 2 parts: There are no fibers in the ECM because if we have fibers in circulating substance (blood for example) it will be clotting in the small blood vessels and the circulation process will stop Connective tissue Fibers: - Collagen fibers: Found in the skin, the most common one, found in the walls, they are a bit flexible. Collagen fiber are more thicker - Elastic fibers: More flexible than collagen fibers and are found in our ears and nose because it contains the core of the elastic fibers. Elastic fibers are thinner than collagen fibers. - Reticular fibers: Are very rare, specialized, can be find in the lymph nodes and in the bone marrow, Ground substance: Non cellular structure does not have any cells. Is a gel-like substance which is mostly water and also contains other molecules like proteins. Rich in proteoglycans, hydrated glycosaminoglycans (GAGs), and multiadhesive glycoproteins. By means of special link proteins, proteoglycans indirectly bind to hyaluronan, forming giant macromolecules called proteoglycan aggregates. The binding of water and other molecules to proteoglycan aggregates regulates movement and migration of macromolecules, microorganisms or metastatic cancer cells in ECM. Connective tissue cells Two different types of cells: - Resident cells: Include fibroblasts (and myofibroblasts) macrophages, adipocytes, mast cells, and adult stem cells. - Wandering (transient) cells: Include lymphocytes, plasma cells, neutrophils, eosinophils, and monocytes. (All these cells are immune system cells). Fibroblasts: Are the principal cells of connective tissue. They are responsible for the synthesis of collagen and other components of the ECM. Macrophages: Are phagocytic cells that contain an abundant number of lysosomes and play an important role in immune response reactions. Other immune system cells: Lymphocytes, plasma cells, neutrophils, eosinophils basophils and etc Adipocytes: Are specialized connective tissue cells that store neutral fat and produce a variety of hormones. Mast cells: Develop in bone marrow and differentiate in connective tissue. They contain basophilic granules that store mediators of inflammation. Adult stem cells: Reside in specific locations (called niches) in various tissues and organs. They are difficult to distinguish from other cells of connective tissue. 2. Classification of CT 3. Histological structure of embryonic CT (mesenchyme and mucous CT) 4 Classifications: Embryonic connective tissue: Mesenchyme is primarily found in the embryo. It contains a small spindle shaped of relatively uniform appearance. Processes extend from these cells and contact similar processes of neighboring cells, forming a three- dimensional cellular network. The extracellular space is occupied by a viscous ground substance. Mucous connective tissue is present in the umbilical cord. It consists of a specialized, almost gelatin-like ECM. Its ground substance is frequently referred to as Wharton’s jelly. The spindle- shaped cells are widely separated and appear much like fibroblasts in the near- term umbilical cord. Some of the cells isolated from Wharton's jelly express significant amounts of mesenchymal stem cells and have the ability to differentiate under adequate conditions into osteocytes, chondrocytes, adipocytes, and neural-like cells. These cells are called Wharton’s jelly mesenchymal stem cells 4. Histological structure of CT proper (loose CT, dense regular and irregular CT) Adult connective tissue Connective tissue proper- can be found in many different places. It includes loose and dense connective tissue Loose connective tissue: It is called loose because it doesn’t have that many components. In most cases the loose connective tissue has fibroblasts and fibrocytes. If you can count the amount of fibers then you know that it is loose. The ground substance is abundant and it occupies more volume than the fibers do. It has viscous to gel- like consistency and plays an important role in the diffusion of oxygen and nutrients from the small vessels that course though the connective tissue as well as the diffusion of carbon dioxide and metabolic waste back to the vessels. Under the epithelium there is loose connective tissue. Dense irregular connective tissue: is characterized by abundant fibers and few cells. Contains mostly collagen fibers, cells are sparse and are typically of a single type, the fibroblast. This tissue does not contain that much ground substance. Because of its high portion of collagen fibers, dense irregular connective tissue provides strength. The structure goes in different direction and are water resistance Dense regular connective tissue: is characterized by ordered and densely packed arrays of fibers and cells. The structure goes in one direction and is water resistant in only that direction. Can be found in ligaments, tendons, aponeuroses. This means that the muscle can only contract in one direction because the fibers are “lined up” in one direction. In dense regular connective tissues there’s different types of connective tissues in it, which are dense irregular connective tissue and loose connective tissue. Epitendineum is a substance that is surrounded by a thin connective tissue capsule. Endotendineum- the tendon is subdivided into fascicles by endotendineum, which is a connective tissue extension of the epitendineum. Aponeuroses: flattened tendons, instead of fibers lying in parallel arrays, the fibers are arranged on multiple layers. The bundles of collagen fibers in one layer tend to be arranged at a 90° angle to those in the neighboring layers. 5. Histological structure of white and brown adipose tissue Specialized connective tissue White adipose tissue: With supporting collagen and reticular fibers forms the subcutaneous fascia, is concentrated in the mammary fat paids, and surrounds several internal organs. Are very large cells with a single, large lipid droplet. It secretes a variety of adipokines, which include hormones, growth factors, and cytokinesis. Every drop is filled with fat. Brown adipose tissue: The cells are not that large. many droplets and not single like white adipose tissue. Can be easily burned because they generate heat in thermogenesis by uncoupling the oxidation of fatty acids in the mitochondria from ATP production. 6. Histological structure of reticular CT Reticular connective tissue: is the stroma of all lymphatic organs for example, spleen, lymph node, hemal node, tonsils. Diffuse lymphatic tissue, solitary lymphatic nodules, and bone marrow is made of reticular connective tissue. This tissue is composed of stellate reticular cells and a complex three dimensional network of reticular fibers. Part 2: Blood 1. Structure of the blood and blood cells Blood is a type of connective tissue that circulates through the cardiovascular system. It consists of protein- rich liquid ECM called plasma and formed elements (WBC and RBC and platelets). There are no fibers in the ECM because if we have fibers in circulating substances (blood for example) it will be clotting in the small blood vessels and the circulation process will stop. Plasma: The ground substance in the blood is plasma which is liquid. Plasma protein consists of albumin (responsible for colloid osmotic pressure), globulins and fibrinogen. Serum: Is the blood plasma but when the blood is clotted. Erythrocytes (RBC): RBC are anucleate which means that they lack a nucleus. There are no nuclei because it's easier to carry around oxygen and carbon dioxide in the body. In the RBC there is an indentation (inbuktning) which makes the entire surface area larger so that means that it can carry around more oxygen and carry away more carbon dioxide around the body, now when the surface area is larger. They have a shape of disks that are packed with hemoglobin. Hemoglobin is a protein that consists of 4 chains of globins with iron containing heme groups for binding, transportation of O2 and CO2. They live for about 120 days, RBC are produced in the bone marrow. In mammals we have the shape of a disk which means no nucleus (anucleate). Chickens, fishes, reptiles has a shape of an egg and they have a nucleus and are much larger than a mammal RBC Leukocytes (WBC) They are divided into two groups: Granulocytes: Has granules is the cytoplasm which are small dots filled with specific substances who are important. They are filled with enzymes who are really important for destroying microorganisms at sites of inflammation. - Neutrophil- no stain. The nucleus is in different segments 1st, 2nd and 3rd. Most common one of all the granulocytes (47% - 67% of all leukocytes). They are dying after fighting the bacteria because they have a small period of living (around a week). The neutrophil phagocytes a bacteria or parasite to kill it. You can tell what kind of gender the organism is based on looking at the barr body of the neutrophil. - Eosinophil- stained with eosin (pink). The nucleus is in 2 segments but the link between the two segments is at one of the ends. Around 1%- 4% of all leukocytes. Are mostly associated with allergic reactions, parasitic infections and chronic inflammation. Eosinophil cannot phagocyte these types of bacteria because eosinophil targets bigger parasites like worms. What they do instead is that they attach themself  on the target and release the granules which are filled with toxic substances which will kill the parasite. - Basophil- stained with hematoxylin (blue). The nucleus is in 2 segments as well but the link between the two segments are in the middle. Less than 0.5% of all leukocytes. Has an important role for allergic reactions for example dust, food, grass. Anoxic shock is when the blood vessels specially the oval blood vessels start making gaps, which leads to that the liquid part of the blood leaves the blood vessels and goes to the surrounding tissues, after that the blood pressure decreases or disappears and the circulation will stop. If this doesn't get treated the patient will die in just a few minutes. Hematoxylin and Eosin are staining the organism with pink and blue, which can help us identify and see what's in the cell for example. Eosin stains the cytoplasm in cells and that's why the cytoplasm is usually in pink. Hematoxylin is staining the nucleus in blue. Agranulocytos: (The A in the beginning of the word means that granules is absent) Has no granules - Lymphocytes: Are divided into many subunits. 26% - 28% of all leukocytes, are the main functional cells of the immune system. They are small cells but with a large nucleus and has no granules T lymphocytes: Involved in the cell- mediated immunity (when viruses are hiding in a cell). If we for example have a virus that has infected a lung cell, this virus is no longer in the liquids and the B lymphocytes can then no longer find the virus because it's hiding in the lung cells. That’s why we have T lymphocytes who check cells if they are okay and if everything is like usual. If a T lymphocyte finds some kind of change in a cell it will send signals to die, that means that the lung cell (in this case) and the hidden virus are dying together. B lymphocytes: Involved in humoral immunity. Humoral means liquids, they are located in the liquids in the lymph and in the blood so they are circulating. They are producing antibodies, which is a very specific protein which is produced for a very specific antigen. The antibodies attach themself to the antigen surface for example the surface of a virus, and will not let the virus infect the cell and this is called opsonization which means that the virus is floating in the liquids (blood) and can not do anything (like infecting other cells) because the virus has to use its receptors to infects cells, but the antibodies are not attached to those receptors which will not make that possible. Natural killer (NK) cells: Programmed to kill certain viruses infected and cancer cells. - Monocytes: Are very large cells and are circulating in the circulatory system including blood vessels. 3%- 9% of all leukocytes. The thing with these cells is that after some time circulating in our body, they will be released into specialized places in  our body tissues. When the monocytes leave the bloodstream they are no longer called for monocytes, they are now called macrophages. - Thrombocytes: Are in birds and reptiles and are nucleated cells, related in function to the platelets of mammals, they are smaller and less elongated than erythrocytes and have a larger, more round nucleus. - Platelets: Are small, membrane- bounded anucleate cytoplasmic fragments, derived from megakaryocytes. - Part 2: Cartilages and bones 1. Classification and structure of cartilages (hyaline, elastic and fibrous cartilage) Cartilage: Composed with 2 components: Cells called for chondrocytes (are called for chondrocytes in cartilage) and ECM. The most important cells in connective tissue are always fibrocytes. More than 95% of all cartilage volume consists of ECM, which is a functional element of this tissue. Cartilage is an avascular structure which means that it doesn't have any blood vessels (the a in the beginning stands for “non”). Cartilage gets oxygen by diffusion of substances bw chondrocytes and blood vessels in the surrounding connective tissue. Three major types of cartilages: The cells in all these three are the same, which is chondrocytes, but the ECM is very different. They all have different fibers in the ECM which will make them have different types of practical work in the body. - Hyaline cartilage: Most common one and makes all the joints and the rib cage and can be found in the respiratory system specially in the trachea, bronchi, larynx and nose. Has type II collagen fibers in the ECM. In Hyaline cartilage, chondrocytes appear in groups of 4, these groups are called isogenous groups and are formed like a circle around each other. Where these isogenous groups are located are called lacunae. The outer layer of hyaline cartilage is called perichondrium and acts like a capsule. The ground substance includes a lot of chemical substances like creatine sulfate, chondroitin sulfate. - Fibrocartilage: Has type I collagen fibers in the ECM. Fibrocartilage is a combination of dense regular connective tissue and hyaline cartilage. Some chondrocytes appear as the elastic cartilage which is in a linear pattern but there are some chondrocytes that go individually. Does not have a perichondrium. This type of cartilage is usually found between bones and that is why it does not have a perichondrium (a capsule). We can find this type of cartilage in the spine, the discs, vertebral bones, menisci of the knee joint. - Elastic cartilage: Has elastic fibers in the ECM. The isogenous groups have a structure as a linear pattern. Can be found in the ears, larynx. Do have a perichondrium Hyaline cartilage Elastic cartilage Fibrocartilage  2. General composition of the bone and structure of bone tissue Bones Are very similar to the cartilages, they are so similar because bones are developing from cartilages. For example, not all species but some cannot walk after birth, there are many reasons but one of them is because they don't have bones they only have cartilages which later develop into bones. In other words, they are under the process of changing the hyaline cartilage to bones. In bones the lacunae are only one cell (osteocyte, os means bone in latin) but in cartilages are in groups of 2-4. The difference bw bone and cartilage is that the bone is a very solid and hard material, the ECM and the ground substance is very solid like a rock, the nutrients like oxygen cannot go through the bone by diffusion as it could in cartilage. The bones structure is like a network because of the canaliculi who are bw every osteocyte and works as a nutrient canal/ tube. In the middle of the osteon there are one bigger canal/tube called Haversian canal, where the nerves and blood vessels are located. Cells of bones: Osteoprogenitor: Cells that are derived from mesenchymal stem cells, they give rise to osteoblast. Osteoblasts: Are very actively producing cells that produce the ECM. When enough ECM are produced osteoblasts become osteocytes. Osteoblasts are making new bones. Bone- living cells: Are cells that remain on the bone surface when there is no active growth. Osteoclast: Are macrophages, who are responsible for remodeling and reorganizing of a bone. Osteoclast is rebuilding what the osteoblasts have been building. 3. Endochondral and intramembranous ossification Bone formation The development from endochondral (a cartilage model serves as the precursor of the cone) or intramembranous ossification (without involvement of a cartilage precursor). Flat bones like the skull are developing directly, mesenchyme differentiates into osteoblastes which then produce the bone structure, so there is no hyaline cartilage in the middle of the process. Develop by intramembranous ossification. Long bones develop by endochondral ossification. Endochondral ossification (the process) Primary ossification center: In the beginning we only have hyaline cartilage, then, under the embryonic period the cells from mesenchyme are going around the hyaline cartilage and making a bony collar (periosteal). This helps maintain the shape of the bone so it doesn't grow in the wrong direction. The next step is that the bony collar is growing deeper into the hyaline cartilage more exactly, in the middle of the bone. We are now starting the development of osteoblasts who can now start producing/ building the ground substance and fiber of the bone. At the same time the osteoclasts migrate as well, they are destroying the hyaline cartilage structure. This process is requiring a lot of energy, which makes the bone need some nutrients, that's why the blood vessels are now migrating as well. After a while we will have 3 ossification centers, and it's here it really becomes like a bone. We can see if the bone growth is over by doing x-rays, if there's still hyaline cartilage inside of the bone that means that it's still growing and the process is not over yet. If there's no cartilage left, it will indicate that this human or animal is now an adult. Intramembranous ossification First we have mesenchyme cells, these mesenchyme cells migrate in different places where the flat bones need to get developed. After the mesenchyme cells transform into osteoprogenitor cells, then these cells transform into osteoblasts where these cells can begin the process of producing bone. Tror inte vi ska ha det här nu på torsdag, det är nog nästa assessment Note: questions of histology of joints will be included in Colloquium No.4 (Anatomy and Histology of Joints)