Histology Flashcards
What is the composition of the cell?
Water – 80% (90% free/ unbound)
Protein – 15%
Define the term organelle and inclusion
Organelle - small, intracellular ‘organs’ with a specific function and structural organisation
Inclusion - dispensable they represent components that have been synthesised by the cell itself,
give some examples of organelles in the cytoplasm
- Mitochondria - (energy production)
- nucleus (Contains genetic code)
- Rough endoplasmic reticulum (protein synthesis)
- smooth endoplasmic reticulum (cholesterol & lipid synthesis/ detoxification)
- Golgi apparatus (modification & packaging of secretions)
- lysosomes (hydrolytic enzymes for intracellular digestion)
What is a cytoskeleton?
determines shape and fluidity, made from thin and intermediate microtubules
What is the function of the plasmalemma?
Provides a selective, structural barrier between the cell and the outside wall
what is the structure of the plasmalemma?
Bimolecular layer of amphipathic (phospholipid phosphate end which is water loving and a fatty acid lipid end which is water hating) phospholipid molecules
Where does the hydrophobic fatty acid chain of the phospholipid molecules face?
Faces towards the middle of the two layers
give examples of integral proteins that the cell inserts into the membrane:
Receptors, channels, transporters, enzymes and cell attachment proteins
The plasmalemma has the ability to exocytose and endocytose material through the cell membrane, explain what this means
Endocytosis is the process of capturing a substance from outside the cell by engulfing it
Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell
What is a vesicle?
Compartments formed by a lipid bilayer separating its contents from the cytoplasm or a fluid-bases extracellular environment
Why are many membrane proteins not distributed equally within the cell membrane?
Many are anchored so not distributed equally
What does it mean when the cell is thought to be selectively permeable?
- highly permeable to water, oxygen, small hydrophobic molecules
- Virtually impermeable to charged ions (Na+)
what does the Plasmalemma’s phospholipid bilayer have embedded in it?
integral and peripheral proteins and cholesterol embedded in it
What are the three main classes of cytoskeletal proteins ?
- Microfilaments
- Intermediate filaments
- Microtubules
Why are actin molecules so dynamic in cytoskeletal elements?
Can assemble into filaments and later dissociate
What is the function of an intermediate filament?
Bind intracellular elements together/to the plasmalemma
What are the classes of intermediate filaments used to identify?
tumour origins
Give some properties of microtubules:
can be assembled/ disassembled
Suggest the importance of microtubules:
Where do they originate from?
Serve as the ‘motorway’ network of the cell
originate from center called centrosome
Describe how the nucleus is enclosed
Nuclear envelope - composed of an inner and outer nuclear membrane with nuclear pores providing continuity with the cytoplasm
What lies in between these two nuclear sheets?
The perinuclear cistern
What is the outer layer of the nucleus studded with and what is it continuous with?
Ribosomes
Rough endoplasmic reticulum
Where is rRNA transcribed?
in the nucleus in a place called the nucleolus (nucleus contains chromosomes)
Describe the two different places in the nucleus that contain DNA
- euchromatin (DNA that is more dispersed and actively undergoing transcription)
- Heterochromatin (DNA that is highly condensed and not undergoing transcription)
Where are ribosomes formed?
Nucleous
How are ribosomes created?
- A small subunit - which binds to RNA
- large subunits - catalyses the formation of peptide bonds
What does reticulum mean?
Net-like structure
What does the ER form?
a network of interconnecting membrane-bound compartments in the cell
What gives rough endoplasmic reticulum its name?
Studded with ribosomes
Describe the vital role the endoplasmic reticulum has
Synthesis of proteins
What is the function of a polysome?
synthesise free floating unpackaged proteins
What is the function of SER?
Continues processing of proteins produced in the RER
Role in the synthesis of lipids
What is the golgi complex composed of?
group of flattened, membrane bound cisternae, arranged in sub-compartments
How do golgi cisterns function?
transport vesicles arrive at the golgi
It modifies and packages macromolecules that were synthesised in the ER
Describe the shape of a mitochondria and describe their composition
- oblong/ cylindrical organelles
- Composed of an inner and outer membrane. Inner membrane is folded to form cristae - which act to increase available surface area
Why are mitochondria different from other organelles?
contain their own DNA and system for protein production
Define intercellular junctions, what type of cells are these particularly prominent in?
link individual cells together into a functional unit - prominent in epithelia
What are the three different types of junction?
1) Occluding junctions - link cells to form a barrier (AKA zonula occludens)
2) anchoring junctions - link sub-membranes actin bundles of adjacent cells (AKA Macula adherens)
3) Communicating junctions - allow movement of molecules between cells (AKA Zonula adherens)
Provide some characteristics of occluding junctions:
- Prevent diffusion
- Appear as a focal region of close apposition between adjacent cell membranes
What do transmembrane cadherins do?
Bind to eachother and to the actin of the cytoskeleton
What are the function of desmosomes?
Link sub-membrane intermediate filaments of adjacent cells (very common in the skin for mechanical stability)
Provide some characteristics of communication (gap) junctions:
- selective diffusion of molecules between adjacent cells
- each junction has a circular path studded with many pores
- found in epithelia
Define a junctional complex:
Close association of several types of junctions found in certain epithelial tissues
list some ways material can move across the cell:
- diffusion
- Via transport proteins (pumps or channels)
- incorporation into vesicles (vesicular transport)
Outline the process of two types of vesicular transport (Endocytosis and phagocytosis)
- Cell membrane invaginates, fuses and the newly made endocytotic vesicle (endosome) buds into the cell,
Exocytosis works in reverse to discharge material
Phagocytosis - Bacterium binds to cell surface receptors triggering extensions of the cell to engulf it forming a phagosome. The phagosome binds with a lysosome carrying digestive enzymes producing a phagolysosome
What is the inner cytosol?
solution of proteins,, electrolytes and carbs
What are the stains used in medicine today?
H& E stain - haematoxylin (purple basic dye) and eosin (pink acidic dye)
What are the four basic tissue types?
Epithelium, connective tissue, muscle and nervous tissue
What are some properties of the epithelium?
- what do they cover and what do they contain?
Covers all surfaces of body, line hollow organs, form glands
all have basal lamina
non-vascular
usually polarised and apical and basal sides differ
Define a few functions of the epithelium
mechanical barrier, chemical barrier, absorption and secretion
What are the different cell shapes of the epithelium?
squamous - flattened, cuboidal - cube and columnar - tall and thin
How do you define a cell according to the number or layers it has?
Simple - one layer
stratified - two or more layers
pseudostatified - appears to have multiple layers
How can you classify a cell according to its surface and tissue specialisations?
prominent microvilli, cillia and keratinised
What are the different glandular epithelia? (endocrine + exocrine)
Endocrine - product secreted towards basal end of cell
distributed by vascular system
DUCTLESS GLANDS
exocrine - product secreted towards apical end of cell - DUCTED GLANDS
Why is connective tissue important?
forms framework of body, dynamic role in development, growth and homeostasis of tissues and energy storage
what are the four types of connective tissue?
Soft connective tissue, hard and blood and lymph
Provide some examples of soft connective tissue
what is the difference between dense regular and irregular
Tendons, ligaments, mesentery,
loose
dense regular = fibres aligned
dense irregular = fibres run in many directions
Hard connective tissue?
bone and cartilage, strong, flexible compressible
What are the 3 types of cartilage?
Hyaline- articular surface, tracheal rings
elastic
fibrocartilage
What is the anatomy of the bone?
outer shell of cortical bone makes up shaft - diaphysis
trabecular bone occupies ends - epiphyses
What some types of connective tissue cells?
o Cells Fibroblasts Adipose cells Osteocytes Chondrocytes
What are muscles and what is muscle force?
- Specialised to generate force by contraction
- Force is movement of actin fibres over myosin fibres
What are the 3 types of muscle?
what are some descriptions of them?
o Smooth – involuntary and non-striated
o Skeletal – voluntary and striated , multinucleated
Nuclei are elongated and located at the periphery, just internal to cell membrane (sarcolemma)
o Cardiac – involuntary and striated
Have intercalated discs – contain multiple intercellular junctions to maintain mechanical integrity
What does nervous tissue consist of? What is its function?
- Consists of neurons and their supporting cells (glia)
- allows for rapid communication between different parts of the body
What is nervous tissue surrounded by?
Give some examples in the CNS and PNS
connective tissue coat - meningies in CNS and epinerium in the PNS
What do astrocytes do?
Support and ion transport
o Oligodendrocytes
Produce myelin
o Microglia
Provide immune surveillance
o Schwann cells (PNS)
Produce myelin and support axons
What are the different salivary glands? - what kind of ducts do they contain?
o Parotid, submandibular, sublingual
o Striated ducts
What are the four major layers of the ailementary canal
mucosa - epithelium(basal lamina), lamina propria(loose connective tissue), muscularis mucosa( thin layer smooth muscle),
submucosa(loose connective tissue),
muscularis externa (inner circular and outer longitudinal layer),
adventitia - outer layer of digestive tract
what is protective mucosa and where is it found?
- Non-keratinised stratified squamous epithelium
o Oral cavity
o Pharynx
o Oesophagus
o Anal canal
What is absorptive mucosa and where is it found?
- Simple columnar epithelium with villi and tubular glands
o Small intestine
secretory muscosa?
- Simple columnar epithelium with extensive tubular glands - stomach
Protective and Absorptive mucosa?
- Simple columnar epithelium with tubular glands - large intestine
What are teniae coli?
outer longitudinal layer is not continuous and is found in 3 muscular strips
What is the nervous system called in the digestive tract?
enteric nervous system
How can you differentiate between bronchus and bronchioles?
o Bronchus – large diameter airways with hyaline cartilage in their wall
o Bronchioles – small airways, no cartilage, mainly smooth muscle
What is the alveoli lined with?
o Lined by simple squamous epithelium
What does blood consist of?
What are some descriptions of RBC and WBC?
55% plasma and 45% cells
RBC = no nucleus - lifespan of 4 months - 7um in diameter
WDC = neutrophils, eosiniphils, basophils, monocytes and lymphocytes
what are the three different layers of arteries? - provide some descriptions of each
tunica intima - extends to internal elastic membrane (endothelium- simple sqaumous epithelium)
tunica media - smooth muscle, extends to external elastic membrane
tunica adventia - supporting connective tissue
What is the structure of an arteriole?
1 or 2 layers of smooth muscle in tunica media and almost no adventitia
What are some properties of capillaries?
endothelial cells and a basal lamina
contain pericyes that are connective tissue cells with contractile properties
What are the three types of capilaries?
fenestrated - pores (gut mucosa, endocrine glands)
continuous - muscle, nerve skin
sinusoidal - large gaps - liver, spleen, bone marrow
What is the structure of a vein and what do venules contain?
Tunica intima, thin continuous tunica media and a few layers of smooth muscle cells
Large veins have thick tunica adventitia
venules - Endothelium and pericytes
When is there the most elastic fibres in the tunica media
In the aorta because smooth muscle has been replaced to allow significantly more stretch
When is a vasa vasorum present?
large arteries - have their own vascular supply due to malnutrition of the the vessel
What is microvasculature?
small arteriole connected to a post capillary venule
precapilary sphincters help control blood flow
In a centrifuge what is the order of cells found from top to bottom?
plasma is found at the top then the red blood cells
what is a neutrophil
What does the cytoplasm of neutrophil contain?
most common leukocyte
cytoplasm contains many granules but these stain poorly with either acidic or basic dyes (neutro)
What type of nucleus does a neutrophil have?
Multi-lobed nucleus
What does the cytoplasm of an eosinophil contain?
prominent granules that have an affinity for red acidic dye eosin(hence eosiniphils)
What is the shape of an eosiophil’s nucleus?
bilobed nucleus
What are eosinophils useful for ?
inducing and maintaining inflammation, particularly in allergic reactions
important in parasitic infection
What is an eosinophil life span?
released from marrow 8-12 hours and then move into tissue where they live
What is the life span of a neutrophil
abundant and short lived so made a lot by bone marrow
What is the cytoplasm like in a basophil?
granules have an affinity for the basic dyes (hence basophils)
What is the purpose of basophils and what does their nucleus look like?
Effector cells in allergic reactions
they have a bilobed nucleus
What are monocytes? - what does their nucleus look like?
precursor of tissue macrophages, largest cell circulating the blood
nucleus often appears kidney bean shaped - non-lobulated nucleus
What is the nucleus like in a lymphocyte?
round nucleus surrounded by thin to moderate rim of cytoplasm that does not have visible granules
Where do T cells differentiate from?
in the thymus
Why are platelets important?
small cell fragments that play a key role in the prevention of blood loss
Where is the main site of blood formation?
In the bone marrow,
