| What is histology? | the study of the microscopic structures of tissues |
| What are tissues? | tissues are a set of differentiated cells that are located in the same region and occupy the same role. |
| What are tissues made up from? | Cells and all elements filling the intercellular and extracellular medium. |
| What are the types of tissues? | Covering tissues (epithelial tissues and glandular epithelial tissues)/ Non-specialized connective tissues and specialized connective tissues (adipose tissue, cartilage tissues, bone tissues and blood tissues)/ Skeletal striated muscle tissue, striated cardiac muscle tissue and smooth muscle tissue/ Nervous tissues of CNS and PNS |
| What is histogenesis? | the differentiation of tissues initially from the embryo (three germ layers). |
| What are the three primitive embryonic germ layers? | Ectoblast, Mesoblast and endoblast. |
| What are the derivatives of the Ectoblast germ layer? | part of the epithelial tissues (epidermis) and the nervous tissue. |
| What are the derivatives of the mesoblast germ layer? | non-specialized connective tissues, cartilage and bone, wall of the heart and vessels, smooth and striated muscles. |
| What are the derivatives of the endoblast germ layer? | covering epithelium lining the intestine, respiratory system and urogenital tract. |
| Do organs only have a certain type of tissues? | No, an organ may contain several varieties of tissues issued from different embryonic cell layers. |
| What are epithelial tissues composed from? | Cells that are tightly packed together with very narrow intercellular spaces, at the limit of visibility under the light microscope. |
| What kind of cells are the epithelial cells? | Polarized, closely juxtaposed, integral with each other through adhesion junctions, involved in one or more physiological functions |
| Where do epithelial cells rest? | On the basal membrane separating it from the connective tissues. |
| Where are the epithelial tissues derived from? | all germ cell layers (ecto, endo and mesoblast) |
| How do epithelial cells differentiate? | morphologically and functionally into two types; covering (surface or lining) epithelia that covers other tissues./ Glandular (with secretory function) specifically involved in the elaboration of secretory product. |
| What are the covering epithelia composed from? | one or more layers of epithelial cells closely juxtaposed with sometimes the presence of non epithelial cells. |
| Where do the covering epithelial cells rest ? | On basal lamina separating them from underlying connective tissues |
| Give three info about the epithelial cells | innervated, non vascularized and have a great capacity for regeneration. |
| What do epithelia cover?, | the surface of the body (the epithelium of the skin is called epidermis) and its natural internal cavities
(---open cavities that extend the inside of the body with the outside (airways, digestive tract,, urinary tract, genital tract) covered by mucosal epithelium
---closed cavities (cardiovascular cavities (vessels are covered by endothelium) and serous cavities (pleural (lungs), peritoneal (abdomen) and pericardial (heart) are covered by mesothelium) |
| Give four characteristics of the epithelial cells | Cohesion (adhesion molecules and specialized junction system attaches epithelial cells and maintain cohesion between these cells and the basal lamina.)/ morphology (because of the juxtaposition of epithelial cells and basal lamina, they either adopt squamous, cuboidal or cylindrical (columnar) shape)
/Presence of intermediate filaments of cytokeratin in their cytoplasm help in polarity/
polarity(Apical pole, Lateral pole and Basal pole) assymmetrical distribution of components of the cytoplasm and of plasma membrane |
| Talk about the Apical pole | it is the domain in contact with the outer environment or faces the lumen of the cavities of the organisms. it's the most specialized since it contains most of proteins neccessary for most organ functions. And has membrane specializations (microvilli, cilia) |
| Talk about the lateral pole | it designates the surfaces that are apposed to neighboring cells, contains proteins necessary for fundamental processes common to all cells. There are anchoring and adhering junctions, and tight junctions connecting them to the apical pole |
| Talk about the basement membrane | resets on basal lamina, hemi-desmosomes and focal adhesion points are obsereved |
| What are the roles of the basement membrane? | polarization of epithelium, mechanically cohesion between the lateral pole and the underlying connective tissue, exchange and filtration processes and control of cellular metabolism. They also exist around some cells (adipose and muscular) |
| What are the criteria of classifications of the epithelial cells? | number of cell layers, shape of the cells, specialization at the apical pole level. |
| Describe morpholigicaly unistratified epithelium cells | consist of one layer of epithelial cells having same size and shape. Apical pole is facing the lumen of the covered cavity, and cells rest on basement membrane. |
| What is the roles of simple epithelial cells? | selective diffusion, filtration, absorption or secretion |
| Where are monostratified epithelial cells mostly found? | areas where risks of wear and injury are low |
| Describe the simple squamous epithelia | they are formed of a thin layer of flattened cells having the same size and shape. the nucleus is elongated, they are often permeable. |
| What are the main functions of the simple squamous epithelia? | filtration, diffusion and osmosis. |
| Where are simple squamous epithelia mainly found? | in the alveolar sacs of the lungs |
| What are the two varieties of simple squamous ? | -endothelial ( cardiovascular system)
-mesothelial (serous epithelium, covering pericardial, pleural and peritoneal closed cavities) |
| what is the main role of endothelium and mesothelium? | Phagocytic role |
| How is the basal lamina of the endothelium and the mesothelium? | sometimes discontinuous with weak tight junctions. |
| What does Juxtaposed mean? | side by side (juxta = next 'latin' and pose = placed 'french' |
| Describe the simple cuboidal epithelium | consist of single layered cuboidal shaped epithelial cells with a spherical central nucleus. The cells are tightly attached to each other. |
| What are the main functions of cuboidal epithelium? | secretion and absorption. |
| Where are simple cuboidal epithilia mainly localized? | at the surface of the ovaries (oviduct) and in the excretory ducts of certain exocrine glands (salivary and pancreas) |
| describe the simple columnar epithelium | cells are elongated and cylindrical, their nuclei are on the same level and located in the basal pole of the cell. |
| What are the functions of simple columnar epithelium? | absorption and secretion. |
| Where are Simple columnar epithelium located | they line the stomach |
| How are simple cylindrical epithelium differentiated? | by the apical pole and what it is attached to (simple columnar- simple ciliated columnar epithelia) |
| What are the main differences between simple columnar and simple ciliated columnar epithelia? | simple columnar with microvilli( apical pole is bordered by microvilli with striated plateau (small intestine) or with a bush boarder.
simple ciliated (vibratile cilia line the fallopian tube) |
| Talk about the pseudo-stratified columnar epithelia | simple epithelia having cells of different sizes but same shape (columnar) nuclei are located in various cites. However all cells rest on the basal lamina in a single layer, but some cells are short and don't reach the lumen, which suggests that tissue have several layers. Absorption and secretion. |
| Talk about pseudo-stratified columnar ciliated epithelium. | cover most of the upper respiratory tract functioning in secretions and transports mucus (includes goblet cells) |
| Where are goblet cells mainly found? | pseudo-stratified and simple columnar epithelium |
| What are stratified epithelial cells? | epithelium consisting of several layers (at least 2) of superposed cells. Basal layer rests on basal lamina and superficial layer is facing the oitside or the lumen, the inner cells are called deep cells. |
| Where are most statified epithelial cells mainly found? | Regions subjected to friction, because they are resistant and able to protect underlying connective tissues. |
| How is the nomenclature of straified epithelial cells? | based on the shape of the superficial cell. |
| What are the characteristics of regions that have stratified squamous epithelium? | most abundant stratified one, observed in places that wear out alot of protection against abrasion |
| Talk about the keratinized stratified squamous epithelium. | they are the superficial layer of skin (epidermis) superficial cells are squamos and accumelate keratin but reject their nucleus and organelles, adapted for dessication (dehydration) forming a resistant and protective surface. |
| Talk about stratified cuboidal epithelium (presence, composition, role, site) | less abundant than squamous, generally composed of two layers and play a better covering role than simple one, found in excertory ducts of sweat glands. |
| Talk about the stratified columnar epithelium | rare, basal layers are made up from irreglar polyhedral cells, only superficial are cylindrical, role of protection and secretion found in urethra |
| where are startified transitional epithelium mainly found? | (it is only found in the urinary system) . |
| Talk about the properties of covering epithelium? | --Renewal: they are exposed to wear and aging lowering their lifespan, they renew by proliferation of stem cells (replacement cells), stem cells divide and the rate of their renewal is different according to epithelium
---Permiability: they act as barriers however their permiability is selective because of the basal lamina (that separates it from chorion), serves as a selective filter. |
| What are malpighian epithelial cells composed from? | Stratified squamous, Composed of several layers of cells thick and well adapted to their protective role, cuboidal or columnar with circular nucleus, they reproduce via mitosis and as we go to the superficial layer they become flat with elongated nucleus, with capacity of regeneration (only upper part) , |
| Where are non-keratinized squamous stratified epithelium found? | they line the inner mouth,vagina and esophaguas (open cavities.) |
| What are urothelium mainly subjected to? | subjected to significant variations in internal pressure and stretching |
| How is the structure of transitional epithelium? | , its thickness is variable according to the distention of the organ; bluky and rounded (empty bladder) squamous and flattened (full bladder ) -they dilate. |
