Histology Flashcards
Eukaryote definition:
Any cell or organism that possesses a clearly defined nucleus
What is the role of the plasmalemma and what does it consist of?
Separates cytoplasm from outside environment, forming a selectively permeable barrier.
Can exocytose and endocytose material.
Consists of:
- Phospholipid bilayer
- Integral proteins
What is the cytosol?
Solution of proteins, electrolytes and carbohydrates which the cellular components are embedded
What is the structure of the nuclear envelope (3)?
Has an inner and outer nuclear membrane with the perinuclear cistern in the middle
Outer nuclear membrane is studded with ribosomes
Has nuclear pores that allow the transport of molecules across the nuclear envelope
Euchromatin and heterochromatin definitions:
Euchromatin: DNA is more dispersed and undergoing transcription
Heterochromatin: DNA highly condensed and not undergoing transcription
Where are different RNAs synthesised?
mRNA and tRNA synthesised in nucleus
rRNA synthesised in nucleolus
Where are ribosomes formed and how do they function?
Formed in nucleolus
Small subunit of ribosome binds RNA, large subunit of ribosomes catalyzes peptide bond formation
Role of RER:
Studded with ribosomes making it responsible for protein synthesis and initiation of glycoprotein formation
Role of SER:
Involved in continuous processing of proteins from RER and lipid synthesis
Structure and role of Golgi apparatus:
Composed of a group of flattened, membrane bound cisternae
Transport vesicles arrive at Golgi from SER; Golgi modifies and packages them
What is the role of the cytoskeleton and what are the 3 main protein filaments?
Consits of protein filaments which allow movement of organelles and also movement of the cell itself
Microfilaments
Intermediate filaments
Microtubules
Structure, function and features of the 3 main protein filaments:
Microfilaments: composed of actin, involved in cellular movement, cytokinesis, endo and exocytosis etc., 7nm
Intermediate filaments: 6 proteins that bind intracellular elements together and to the plasmalemma, >10nm
Microtubules: composed of ⍺ and β tubulin, originate from centrosome, polar, dynein and kinesin attach and move along them, 25nm
What are the 3 modes of cellular transport and how do they work?
Endocytosis: membrane invaginates, fuses, newly made endocytic vesicle buds into cell, often receptor mediated.
Exocytosis: works in reverse to endocytosis
Phagocytosis: bacteria engulfed and digested
What are occluding junctions:
Intracellular junctions that link cells to form a diffusion barrier
Also known as tight junctions or zonula occludens
Function of anchoring junctions and the 3 types:
Provide mechanical strength
Adherent junctions: link submembrane actin bundles of adjacent cells via cadherin molecules
Desmosomes: link submembrane intermediate filaments of adjacent cells
Hemidesmosomes: link submembrane intermediate filaments of cells to extacellular matrix through transmembrane proteins
What are Communicating junctions (gap junctions)?
Intracellular junctions that allow movement of molecules between cells
Each junction is a circular patch studded with pores
What do haemotoxylin and eosin do?
Haematoxylin stains acidic molecules purple
Eosin stains basic molecules pink
Structure of epithelium:
Cover surfaces of the body, lines hollow organs, forms glands
Backed by a basal lamina (basement membrane)
Non-vascular
What is the basal lamina?
A thin layer of specialised extracellular material between the basal surface of epithelial cells and the underlying tissue
Apical and basal definitions:
Apical: faces the lumen of a tube or the external environment
Basal: attaches to the basement membrane
Functions of epithelium:
- Mechanical barrier
- Chemical barrier
- Absorption
- Secretion
- Containment
- Locomotion
Pseudostratified definition:
Multiple layers, all in contact with basal lamina
Cell/tissue surface specialisations:
- Microvilli
- Cilia
- Keratinized
Endocrine and exocrine glands function:
Endocrine: Product secreted towards basal end of cell and distributed by vascular system - ductless
Exocrine: Product secreted towards apical end of cell - ducted