Histology Flashcards
What are the different shapes of epithelium?
Cuboidal, Squamous (flat), Columnar
What are the characteristics of epithelial tissue?
Shape, Layers, Keratinization
What are the different layering types for epithelial tissue?
Simple (single layer), Stratified, Pseudo-stratified
What are the types of connective tissue?
Loose, Dense, Reticular, Adipose Tissue, Specialized (cartilage, bone, blood)
What are some examples of connective tissue?
Fibroblasts, Adipocytes, Mast cells, Macrophages, Pericytes, other white blood cells
What is the function of loose connective tissue? Give an example.
Packing material found throughout the body. Also serves to provide nutrition to epithelium. Ex: submucosa in intestines
What do fibroblasts do?
Collagen release
What is role of elastin in the aorta? In lungs?
Allow for stretching of aorta to allow for increased blood flow. In lungs, elastin allows for expansion of lungs when breathing
What are the muscle types?
Skeletal, Cardiac, Smooth
Which muscle types are striated? Which muscle types are non-striated?
Striated: Cardiac, Skeletal Non Striated: Smooth
What is the structure of a muscle fiber?
Myocytes made of many muscle fibers. Muscle fibers made of sarcomeres which are made of alternating thick and thin filaments. Thin filaments made of actin, troponin, tropomyosin. Tropinin binds the thick filament and causes contraction using ATP as power source.
What is the role of calcium in muscle contraction?
Calcium is released from the sarcoplasmic reticulum after muscle excitation. The calcium binds to the thin filaments and exposes the binding site for the myosin head on the THICK filament to bind and cause contraction.
What is are the differences between cardiac muscle and skeletal muscle?
1) cardiac myofibrils tend to much shorter in length and also tend to branch
2) nuclei of cardiac myocytes are more centered vs off to the side in skeletal muscle
3) cardiac myocytes are also connected to each other at their ends using “intercalated discs”
What is the purpose of intercalated discs?
Intercalated discs are specialized intercellular junctions that propagate depolarizations from cell to cell. Signal generated by SA node and propagated throughout heart using interacalated discs.
What are the key characteristics of smooth muscle histology?
1) Bright pink (eosinophilic cytoplasm)
2) blunt-ended nuclei (cigar shaped)
What is the purpose of Schwann cells? What is the CNS equivalent?
Myleination of axons
Oligodendrocytes
What stain is used for myelinated axons?
Osmium staining
How can you identify cardiac muscle?
How can you identify cardiac hypertrophy?
1) Myofibers are shorter and branch
2) Nuclei are central
3) Cells attach to each other via intercalated disc.
Cardiac hypertrophy -> significantly increased branching of myocytes
What is the endoneurium? Perineurium? Epinerium?
- The endoneurium is the loose connective tissue surrounding each individual neuron
- The perineurium is the specialized connective tissue surrounding each nerve fascicle (bundle of neurons). The perineurium contains tight junctions and contributes to the blood-brain barrier.
- The epineurium includes dense irregular connective tissue that surrounds a group of nerve fascicles and fills the spaces between nerve fascicles.
Where are hemidesmosomes located?
Hemidesmosomes are located on the basal side of epithelial cells. They are responsible for anchoring the epithelial cell to the basement membrane (using keratin intermediate filaments) and also help provide nutrtion from the basement membrane to the epithelial cell.
Hemidesmosomes bind to collagen type 4 in the basement membrane)
**** Certain skin blistering diseases are the result of an absence of hemidesmosomal proteins. In bullous pemphigoid, autoantibodies against hemidesmosomal proteins induce sepeartion of epithelium of skin from connective tissue.
What are the thick and thin filaments made of in skeletal muscle?
What about in smooth muscle?
The thing filaments in skeletal muscle is made of troponin, actin, and tropomyosin.
In smooth muscle, since it operates via the calmodulin, myosin light chain kinase pathway, the thin filaments are ONLY made of actin filaments. The myosin light chian kinase phosphrolyates the myosin chains, allowing it to bind to actin filaments.
What are the rectus abdmoninus muscles? Which direction do the striations go?
Abdominal muscle (where the abs are)
What does loose connective tissue look like under the microscope?
Few fibers, often has high fat content, high ground substance (polysacchirde matrix) which give white appearance after staining
What does densely packed connective tissue look like?
Densely packed fibers with collagen fibers in a matrix. Dense connective tissue can either be irregular (woven and multidirectional) or regular (parallel collagen fibers).
Example of dense irregular connective tissue = dermis and in deep fascia
What is ground substance primarily made from?
The ECM contains fibers (collagen or elastin) that are suspended in a gel-like substance called ground substance. A primarily ingredience of ground substance is glycosaminoglycans, whose negative charges bind water. This keeps the ECM hydrated.
Overall, the matrix provides mechanical support, hydrates the tissue, and via GAGs which brind to cell membranes and growth factors, it plays a dynamic role in regulating cell migration and reaction of cells to their extracellular environment.
Ground substance is also made of proteoglycans, which have GAGs attached to a lienar core protein.
Finally, ground substance have multiadhesive glycoproteins, which help stabilize connective tissue and allow for binding of the basal cell membranes of epithelia.
