Histology Flashcards
Define histology
What does it help us understand?
histology is the science of microscopic structure of cells, tissues and organs.
It helps us understand relationship between structure and function
label the organelles of the cell (from slides)
plasma membrane
cytoplasm
RER and SER
Golgi apparatus
ribosomes
mitochondria
nucleus
nucleolus
lysosomes
centrioles
microvili
vacuoles
What is a cell?
- a cell is the smallest functional unit of an organism that can function independently
List the membranous and non-membranous organelles?
membranous: mitochondria, Golgi apparatus, endoplasmic reticulum
non-membranous: ribosomes, nucleolus, centrioles
Describe the nucleus
- “brain” of the cell
- houses information about every structure and process of the cell and organism, in the form of DNA
- DNA is condensed and coiled up into chromosomes
- consists of chromatin (hetero and eu-chromatin) which is made up of DNA wrapped around histone proteins
Describe the plasma membrane
- semipermeable 2 layered membrane
- serves as a dynamic medium for cell’s interaction with external environment
- controls everything that comes in or out of the cell
- phospholipid bilayer, selective permeability (amphipathic, has both hydrophobic and philic parts)
- contains cholesterol
- contains protein channels, carriers and receptors
2 types of cells and what the living organisms they include
- eukaryotic: animals, plants, algae and fungi
- prokaryotic: bacteria, archaea
describe the cytoplasm
semi-solid medium that keeps organelles suspended and nutrients dissolved within internal cellular environment
describe mitochondria
- for energy (ATP) production
- consists of inner membrane, intermembrane and outer membrane
Describe ribosomes
function: protein synthesis
composed of a small and large subunit
Describe:
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
- ribosomes bind to it
- it stores proteins
- is the extension of the nuclear membrane
- lacks ribosomes
- a collection of independent sacs or continuation of RER
- synthesizes lipids, steroids and phospholipids
Describe golgi apparatus
- protein storage centre
- divided into cis nd trans components
Describe 3 types of vesicles
- exocytotic: content will be expelled
- lysosomal: protein digestion and defence
- secretory: for regulated expulsion of content in response to a stimulus
How do tissues form?
4 main tissue types
cells come together with extracellular matrix (jelly-like fluid)
- connective
- muscle
- nervous
- epithelial
Functions of epithelial tissue
- secretion
- protection
- provides surface for absorption, excretion and transportation of molecules
- special sensory receptives
- barrier against mechanical injury, invasive microorganisms and fluid loss
- provides low friction surface covering
Describe epithelial tissue
- examples
- structure
examples: skin, digestive system lining
stratified, several layers
- thin sheets of tightly packed cells within a thin ECM
- one side of epithelium exposed to air or internal fluid and other side attached to basement membrane and a dense mat of connective tissue
Describe the different cell types of epithelial tissue classified based on shape + draw
- squamous epithelial: cells appear squashed/flattened. Cells are wider than they are tall with an oval shaped nucleus
- cuboidal epithelial: square shaped cells, they have a similar width to height ratio. Nucleus is large, round and centrally located and the cytoplasm is rich with organelles
- columnar epithelial: rectangular column shape, they’re taller than they are wide. Nucleus is also elongated having a long oval shape. Organelle rich cytoplasm. Can have apical projections like microvili or cilia. They can be modified to produce mucuous or other secretions or they for specialised sensory receptors
Describe different epithelial tissue types based on number of layers
simple: one layer of cells
stratified: multiple layers
Describe sub-classifications of epithelium based on cell specializations
- pseudostratified epithelium: simple columnar epithelium but appears to have multiple layers.
All the cells are attached to the basement membrane but they don’t all reach the free surface, thus forming a sheet of cells with different heights and irregularly located nuclei - some have cilia (upper respiratory pathways, uterine tubes)
- stereocilia (epididymis)
- or without any apical specializations (ductus deferens)
- transitional epithelium: stratified epithelium found in organs able to distend (swell).
Called transitional as its superficial cells can change their shape (from cuboidal to squamous) when the organ stretches
featured in some parts of urinary tract: renal calyces, ureters ad urinary bladder (urothelium)
Epithelial cells are the building blocks of epithelial tissue. Describe the 3 regions of epithelial cell membranes
apical, lateral and basal
this is called membrane polarity
Apical specializations are different types of fingerlike cytoplasmic extensions of the apical surface. They differ in their length, motility and function. What are the three types of specializations?
Microvilli - are microscopic protrusions of the cell membrane which mainly function to increase the apical surface area for absorption. Large quantities of microvilli form a ‘brush border’, due to appearance. The enterocytes of the small intestine has such specializations to facilitate absorption of food in the gut.
Stereocilia - a type of microvilli, but they’re immotile and longer. Their functions are absorption (epididymis and ductus deferens) and mechano-sensory reception (inner ear)
Cilia - fingerlike structures present on almost every epithelial cell.
3 types of cilia:
motile: removing foreign particles from the epithelial surface
non-motile (primary): transportation of signals from the ECM to the intracellular space
nodal: fetal development
Name the top and bottom of epithelial tissue
top: apical surface
bottom: basal surface
Describe connective tissue
examples: bone, tendons, blood
various types of cells and fibres held together by a matrix (liquid, solid or a gel)
function: support and insulation
Describe muscle tissue
examples: muscles that make bones move, heart, muscles surrounding digestive tract
bundles of long cells (muscle fibres) that contain specialized proteins capable of shortening or contracting
