Histology - Cardiovascular/Respiratory Flashcards
What is blood? What is it made up of?
Blood is fluid connective tissue. Cellular component = 44% (erythrocytes = 43%, leucocytes = 1%) + fluid component (plasma = 56%)
What is plasma? What is it made up of? What is serum?
Plasma = blood minus the cells. Made up of water, salts + minerals, plasma proteins (albumin etc.), hormones + clotting factors. Serum = plasma minus clotting factors
What are erythrocytes? What is their shape? Where are they created and destroyed? How is the cell shape maintained?
Erythrocytes = red blood cells. 4 to 6million per mL of blood + last for 4 months. Anculeate, biconcave discs, 6.5-8.5 um in diameter, haemoglobin = major protein. Created in liver (foetus) + bone marrow. Destroyed in liver + spleen. Cell shape maintained by endoskeleton attached via major protein called spectrin.
What are the 3 categories of leucocytes (white blood cells)? What types of white blood cells are in each category?
- Granulocytes (contain visible granules):
- Neutrophils (40-75%)
- Eosinophils (-5%)
- Basophils (-0.5%)
- Agranulocytes (no visible granules):
- Lymphocytes (20-50%)
- Monocytes (1-5%)
- Platelets (cell fragments, not cells)
What are neutrophils? How do they appear? What is their role?
- Commonest white blood cell + granulocyte
- Multi-lobed nucleus, granular cytoplasm, 12-14um in diameter, contain myeloperoxidase (needed in order to conduct respiratory burst to engulf macromolecules)
- Primary phagocytes = engulf + destroy foreign macromolecules
- Circulate in blood + invade tissue spaces
What are the 3 types of cytoplasmic granule?
- Primary = lysosomes, contain myeloperoxidase + acid hydrolases
- Secondary = contain specific substances secreted to mobilise inflammatory mediators
- Tertiary = contain gelatinises (break down proteins) + adhesion molecules. Aid neutrophil out of blood vessel + through tissue
What are eosinophils? How do they appear? What is their role?
- Make up 1% of total number of white blood cells, numbers increase in parasitic infections
- Bi-lobed nucleus, 12-17um in diameter, distinctive large red cytoplasmic granules with crystalline inclusions
- Play a role in phagocytosis + response to allergens but have antagonistic action to basophils + mast cells
How do eosinophils appear under an electron microscope?
- Have lozenge-shaped granules with crystalline cores
- Particular affinity for antigen/antibody complexes
- Have receptors for immunoglobulin E on surface
- Inhibit mast cell secretion + neutralise histamines, so important role in infammatory responses
What are basophils? How do they appear? What is their role?
- 0.5% of white cells
- 14-16um diameter, bi-lobed nucleus + prominent dark-blue staining cytoplasmic granules (contain histamine)
- Involved in inflammatory reactions + act to prevent coagulation and agglutination
How do basophils appear under an electron microscope? What are they thought to be the circulating form of?
- Have receptors for IgE, release histamine = results in immediate hypersensitivity reaction (anaphylaxis)
- Thought to be circulating form of mast cells
What are the two types of lymphocytes?
- Lymphocytes = small + appear mainly as nucleus. Two types:
- B cells = become plasma cells + secrete antibodies. Develop in bone marrow
- T cells = involved in cell-mediated immunity. Develop partly in thymus
- You cannot distinguish between T and B cells. All lymphocytes look the same on H&E
What are the 3 types of T cells? What are NK cells?
- T Helper (TH) cells = help B cells + activate macrophages
- T Cytotoxic (TC) cells = kill previously marked target cells
- T Suppressor (TS) cells = suppress TH cells, so suppress immune response
- Natural Killer (NK) cells = mainly kill virus infected cells
What are monocytes? How do they appear? What is their role?
- Immature cells, circulate briefly in blood
- Reniform (kidney) shaped nucleus, 15-20um diameter
- Differentiate into one of several cell types within tissue, some become antigen presenting cells so pass antigen fragments to lymphocytes
- Major phagocytic + defensive role
- Although agranular, have small cytoplasmic granules
What do monocytes differentiate into?
- Tissue macrophages = everywhere
- Kupffer cells = liver
- Osteoclasts = bone
- Antigen presenting cells = everywhere
- Alveolar macrophages = lung
What are platelets? Where do they derive from? How do they appear? What is their role?
- Fragments of cells derived from megakaryocytes in bone marrow
- 1-3um diameter, surrounded by cell membrane + contain vesicles with coagulation factors
- Responsible for clotting of blood
What is haematopoesis? Where do all blood cells stem from? What does this stem into? What do these two cells eventually give rise to?
Formation of blood cells. All stem from multipotential haematpoetic stem cell (haemocytoblast). Goes to common myeloid progenitor + common lymphoid progenitor. Common myeloid progenitor results in platelets, erythrocytes, mast cells, basophils, neutrophils, eosinophils + monocytes. Common lymphoid progenitor gives rise to lymphocytes. Don’t need to know whole table
Image of bone marrow.
- Bony trabeculum = piece of haematopoietic bone marrow (long, pink)
- Adipocytes = white empty spaces
- Haematopoietic stem cells = inbetween adipocytes
Where do all blood cells come from in adults? What are the 3 types of haematopoeitic stem cells?
All blood cells from in haematopoeitic bone marrow (not in children). Myelon = lies next to bone + give rise to white blood cells, erythron = lies inbetween bony trabeculae + give rise to red blood cells, megakaryocytes = lies in between bony trabeculae + give rise to platelets
What happens in erythropoeisis? What is it mediated by?
Erythropoeisis = forming erythrocytes. Proerythroblast to reticulocyte (step just before production of red blood cells). Cell matures + reduces in size, Hb increased (early = basophilic, later = eosinophilic), loss of organelles. In final stage, nucleus is lost. Mediated by the hormone erythropoeitin (EPO)
What happens in granulopoeisis?
Granulopoeisis = formation of granular cells, similar for neutrophils, eosinophils + basophils. Increasing number of granules, increasingly complex shape of nucleus. Bone marrow contains large pool of stored mature neutrophils to be released during times of infection. Lymphocytes = only mature blood cells capable of cell division
What proportion of of blood cells are white?
- A. 56%
- B. 75%
- C. 10%
- D. 43%
- E. 1%
E
Where are these cells formed in adults?
- A. Bone marrow - phalanges
- B. Bone marrow - ribs
- C. Liver
- D. Spleen
- E. Thymus
B
Which is the predominant leukocyte?
- A. Basophil
- B. Eosinophil
- C. Lymphocyte
- D. Monocyte
- E. Neutrophil
E
Numbers of which cell type increase in patients with worms?
- A. Basophil
- B. Eosinophil
- C. Lymphocyte
- D. Monocyte
- E. Neutrophil
B
Where do B-lymphocytes mature in adults?
- A. Blood
- B. Bone marrow
- C. Bowel
- D. Brain
- E. Bursa of Fabricus
B
Which statement regarding this cell is true?
- A. Contains Charcot-Layden crystals
- B. Has IgE receptors
- C. Produces histamine
- D. Phagocytosis bacteria
- E. Secretes antibodies
B and C
Which statement concerning this cell is true?
- A. It has IgE receptors
- B. It neutralises histamine
- C. It secretes antibodies
- D. It’s the most abundant leucocyte
- E. It will become a mast cell
Monocytes become which of the following?
- A. Chondroblasts
- B. Fibroblasts
- C. Hepatocytes
- D. Kupffer cells
- E. Osteophils
D
Which of these is the multipotential haematopoeitic stem cell?
- A. Haemocytoblasts
- B. Megakaryocyte
- C. Myeloblast
- D. Promyelocyte
- E. Reticulocyte
A
Which of these gives rise to platelets?
- A. Haemocytoblast
- B. Megakaryocyte
- C. Myeloblast
- D. Promyelocyte
- E. Reticulocyte
B
Which of these statements concerning erythropoeisis is true?
- A. Early precursors are eosinophilic
- B. It occurs away from bony trabeculae
- C. Nuclear shape becomes increasingly complex
- D. Organelle numbers increase
- E. The cell gets progressively larger
B
What are the layers of the heart?
- Pericardium
- Epicardium
- Myocardium
- Endocardium
What is the pericardium?
Outermost layer of the heart, layer of mesothelial cells resting on thin layer fibrous connective tissue. Visceral pericardium = layer on outer surface of heart, parietal pericardium = layer of cells on inner surface of fibrous sac containing heart
What is the epicardium?
Underneath pericardium, layer of fatty connective tissue, contains mixture of vessels + nerves
What are intercalated discs?
Connect adjacent cardiac myocytes. Contain gap junctions, adhering junctions + desmosomes
What is endomysium?
Loose fibrous connective tissue between myocytes, may contain small number of lymphocytes
What is the size of atrial myocytes compared to those in the ventricles? What type of an organ is the heart? What hormone does it secrete?
Atrial myocytes = smaller than those in ventricle as have to pump against a much lower pressure. Heart is an endocrine organ that secrets atrial natriuretic peptide, which can be seen in the myocardium of the atria. Myocytes of ventricles do not secrete atrial natruiretic peptide
The rhythmic beating of the heart is the result of a coordinated contraction that’s initiated through the cardiac conduction system. What makes up the conducting system? Where can we find Purkinje fibres?
Sinoatrial node (iniated here), electrical impulses pass across atrial myocardium to atrioventricular node. Then passes through Bundle of His + then through Purkinje fibres (subendocardial). We find Purkinje fibres in ventricles immediately below endocardium, but difficult to appreciate in H&E. Image = PAS, highlights the glycogen rich cytoplasm in a deep magenta
What is the endocardium?
Innermost layer of heart, formed by thin layer of fibrous connective tissue lined on its inner surface by single flat layer of endothelial cells
What does the endocardium also cover? What are these structures all connected to and what 3 layers do they comprise?
Covers the cardiac valves (specialised structures that regulate direction of blood flow). All connected to central fibrous body which forms the skeleton of the heart. Fibrosa (dense fibrous CT), spongiosa (loose fibrous CT) + ventricularis (collagen + elastic fibres)
What is the primary function of these cells?
- A. Contraction
- B. Store glycogen
- C. Secrete atrial natriuretic peptide
- D. Secrete nitric oxide
- E. Transmit electrical impulses
E
Where in the heart can these cells be found?
- A. Beneath the endocardium
- B. In the chordae tendinae
- C. In the epicardium
- D. In the mitral valve annulus
- E. In the sinoatrial node
A
What are the functions of the respiratory tract?
- Filtration
- Humidification
- Warming
- Olfaction (and taste)
- Gas transport
- Speech
- Protection against infection
- Gas exchange
Respiratory system is largely lined by respiratory epithelium. What is its structure?
- Lines tubular/conduction part of respiratory system
- Pseudostratified columnar ciliated epithelium, all cells in contact with basement membrane (nuclei at different heights)
- Contain ciliated epithelial cells + interspersed goblet cells
What is the function of the nose? What is it lined by?
- Serves to filter, humidify + warm the inspired air + also site of olfaction.
- Front of nostrils lined by keratinising stratified squamous epithelium
- Back of nostrils lined by non-keratinising stratified squamous epithelium
- Nasal cavity lined by respiratory epithelium
- Connective tissues underneath respiratory epithelium comprise loose fibrous connective tissue containing seromucinous glands + rich network of blood vessels
What is the epithelium like in the roof of the nasal cavity? How can we distinguish between olfactory and respiratory epithelium?
- Olfactory epithelium (pseudostratified columnar ciliated epithelium), but absence of goblet cells. Contains population of basal cells, all cells are in contact with basement membrane. Also contains bipolar neurons whose dendrites reach surface of epithelium.
- Olfactory epithelium has serous glands of Bowman underneath basement membrane (secrete fluid that helps to wash surface). Also has large number of nerves in this underlying connective tissue
What is the nasopharynx lined by? What is its function?
- Nasopharynx lined by respiratory epithelium
- Used for gas transport + to humidify + warm inspired air
What are the nasal sinuses? What is their purpose? What are they lined by?
- Air filled spaces within the bones of skull and facial skeleton
- Lower weight of front of skull, add resonance to the voice, humidify + warm inspired air
- Lined by respiratory epithelium
What is the larynx? What is it made of and lined by?
- Larynx (voice box) = cartilaginous box, site of voice production
- Nearly all formed by hyaline cartilage (hold larynx open against negative pressure during inspiration)
- Lined by respiratory epithelium (except vocal cords). Below this is loose fibrocollagenous stroma with lymphatics, blood vessels + seromucinous glands. Hyaline cartilage = blue dots behind perichondrium
The vocal cords are found within the larynx. What are they lined by?
Not lined by respiratory epithelium, instead lined by stratified squamous epithelium that overlies loose irregular fibrous connective tissue (occupies virtual space known as Reinke’s space). Blood vessels but almost no lymphatics
What is the function of the trachea? What is made of and lined by?
- Conducts air to + from lungs
- Made of C-shaped cartilaginous rings + lined by respiratory epithelium. Underneath there is seromucinous glands in submucosa, perichondrium, C-shaped rings of hyaline cartilage, perichondrium + then loose connective tissue
Where are Clara cells found? What do they contain? What is their function?
- Most numerous in terminal bronchioles (not last bronchioles, last part of conducting airways, give rise to first part of distal respiratory tract)
- Contain mitochondria, smooth ER + secretory granules
- No cilia, cytoplasm appears pale
- Function uncertain
What are respiratory bronchioles? What is their function? What are they lined by?
- First part of distal respiratory tract, link terminal bronchioles + alveolar ducts. Gas exchange + transport.
- Lined by cuboidal ciliated epithelium, walls have spirally-arranged smooth muscle, no cartilage
Image showing bronchus, bronchiole, respiratory bronchiole and alveolar duct.
Alveolar ducts branch into alveoli
What are the alveoli?
- Site of gas exchange within lungs (100-400 million per lung). Each alveolus = 250um diameter
A number of different cells can be found within the alveoli. What is most of the surface area of the alveolar wall lined by?
Type I pneumocytes. Squamous epithelial cells (flattened nucleus + few organelles). 40% of cell population but 90% of surface area
What are type II pneumocytes? What do they contain? What do they produce?
Make up 60% of cell population but 5-10% surface area. Rounded cells, round nucleus, rich in mitochondria + smooth and rough ER. Produce surfactant (protein which acts to lower surface tension in lungs, makes it easier to inflate)
What are the alveolar macrophages? Where are they found? What is their function?
- Luminal cells, also present in interstitium
- Phagocytose particulates including dusts + bacteria
- Once undertaken phagocytic role, can be removed via lymphatics or mucociliary escalator
What is the alveoli blood-air barrier made of?
- Type I pneumocyte which rests on basement membrane shared by endothelial cell of adjacent capillary (very thin, 200-800nm), can say there’s different amounts of layers depending on what you count. I would say 4 (surfactant, type I pneumocyte, basement membrane + vascular endothelial cell)
In some parts of alveolar wall, there is interstitial tissue. What is it comprised of?
Loose fibrous connective tissue comprised of collagen + elastin fibres, fibroblats + macrophages. Holes are called pores of Kohn (help lungs to inflate easily + evenly during inspiration). Pores of Kohn equalise pressure but allow pathogens to spread
There two layers of pleura: one adherent to outer surface of the lungs, one adherent to inner surface of chest wall. What are they made of?
Single layer of squamous epithelial cells (mesothelial cells), rests on loose fibrocollagenous connective tissue (has inner layer of elastic tissue, layer of fibroconnective tissue in middle + outer layer of elastic tissue)
Which part of the respiratory system is this?
A. Frontal sinus
B. Parietal pleura
C. Roof of nasopharynx
D. Terminal bronchiole
E. Trachea
C
How many cell layers are there in the air blood barrier?
A. 1
B. 2
C. 3
D. 4
E. 5
B. Note it says cell layer, not cell. Basement membrane isn’t a cell
