Histology

• Muscle tissue is responsible for movement and generating force.
• Cells are the smallest unit of living matter and there are about a trillion of them inside the human body, including red blood cells, brain cells, muscle cells, and bone cells.
• Tissues are a group of common cells organized for a common purpose, and there are four basic tissues in the body: epithelium, connective, muscle, and nervous.
• An organ is a group of tissues organized for a common purpose, and organs like the heart, lungs, stomach, kidneys, and so on, are grouped into organ systems.
• An organism is a group of organs organized for a common purpose, and all organisms are made from the four basic tissues: epithelium, connective, muscle, and nervous.
• Histology is the study of tissues, including epithelium, connective, muscle, and nervous, and it's miraculous because these are the materials that everything in the body is made from.
• Hematoxylin and eosin (H&E) stain is the most widely used stain in histology and pathology, and it stains the nucleus purple and proteins pink.
• Connective tissue proper is composed of fibroblasts, which synthesize the extracellular matrix, and adipocytes, which store lipid in a single droplet.
• Connective tissue is composed of four different types: connective tissue proper, cartilage, bone, and blood.
• Respiratory epithelium is located primarily in the trachea and bronchi, also known as the bronchial tree.
• Transitional epithelium or urinary epithelium has more than one layer of epithelial cells.
• Transitional epithelium is found only in the urinary system, specifically in the ureter, bladder, and proximal urethra.
• The apical layer of transitional epithelium are dome-shaped or festoon-shaped and stretch and permit the dispersion of a urinary organ from an empty bladder to a full bladder.
• The function of pseudostratified ciliated columnar epithelium is secretion, mainly mucus and the propulsion of mucus by the cilia to the outside of the body.
• Pseudostratified ciliated columnar epithelium has cells that appear to lie on top of each other, but every cell is anchored to the basement membrane, hence the term 'pseudostratified'.
• Epithelium forms glandular tissue and lines the lumen of tubular organs and body cavities, and it also externally covers the body and organs.
• Osteoblasts build bone tissue, osteocytes maintain bone tissue, and osteoclasts break down bone tissue.
• Smooth muscle tissue is involuntary, non-striated, and the nuclei in smooth muscle often look like a corkscrew in longitudinal section and are centrally located in cross section.
• Cardiac muscle tissue is involuntary, has intercalated disks, and its location is in the wall of the heart, also known as myocardium.
• The extracellular matrix of bone is calcium and phosphate.
• The extracellular matrix of bone contains osteocytes, which are mature osteoblasts surrounded by bone matrix.
• Muscle tissue is comprised of contractile type cells and there are three types of muscle tissue: skeletal, cardiac, and smooth.
• Red blood cells transport oxygen, white blood cells are for immune defense, and platelets are for helping to clot blood.
• The extracellular matrix of blood is plasma, water, and clotting factors.
• Skeletal muscle tissue is voluntary, the muscle fibers are long and striated, and it is compartmentalized by connective tissue sleeves.
• Epithelium consists of cells that are anchored to a basement membrane and have apical and basal surfaces.
• Epithelium has no extracellular matrix (ECM) and the tissue is avascular, meaning there are very few if any spaces between cells and as a result, there are no blood vessels.
• The basement membrane anchors epithelium to the underlying connective tissue where the capillaries reside.
• The epidermis is keratinized and when you see the skin those apical layers are keratinized with which means all of the cells are filled with keratin and they're dead and they get rid of the nucleus and organelles to make room for keratin.
• The location for stratified squamous epithelium is any place you need protection from abrasion like the epidermis, the outside layer of skin or the esophagus and the vagina.
• Stratified squamous epithelium consists of more than one layer of cells with one layer touching the basement membrane and the apical surface of apical layer cells are flat and it's epithelium.
• Simple columnar epithelium is ideal for reabsorption or absorption like you'd have in the intestine or secretion like you'd have in also the intestines or your airways of the bronchi.
• Stratified squamous epithelium is ideal for protecting underlying tissue from abrasion and often these cells have keratin.
• Simple cuboidal epithelium functions include absorption and secreting substances.
• Simple columnar epithelium is often lined with microvilli and cilia.
• Simple columnar epithelium consists of one layer of tall, thin cells with the nuclei either being round at the base or a narrow nucleus and it's epithelium.
• Simple squamous epithelium functions include absorption and secreting substances.
• The esophagus or vagina is non-keratinized stratified squamous epithelium so you'll see nuclei all the way to the apical surface.
• Simple cuboidal epithelium consists of one layer of cube-shaped cells with the nuclei centrally located and epithelium.
• A simple squamous epithelium consists of one layer of flat cells with a centrally located nucleus.