Cells and tissues -Dr Felts Flashcards
(107 cards)
1
Q
Describe the features of the plasmalemma.
A
Separates the cytoplasm and outside environment
It is fluid, can change shape easily and is selectively permeable. (Highly permeable to small hydrophobic molecules but not to charged ions)
It is a phospholipid bilaterally with integral proteins, peripheral proteins and cholesterol integrated in it.
2
Q
What does the plamalemma being amphipathic mean?
A
It has hydrophobic heads at the outer and inner surfaces and hydrophobic fatty acids in the centre
3
Q
The plasmalemma can exocytose and endocytose what does this mean?
A
Exocytose = send materials out of the cell Endocytose = bring materials into the cell
4
Q
What is the difference between organelles and inclusions?
A
Organelles = small intracellular ‘organs’ essential to life Inclusions = only present in some cells not all
5
Q
What are the three classes of filament that make up the cytoskeleton ?
A
Microfilaments
Intermediate filaments
Microtubules
6
Q
Describe microfilaments.
A
Composed of actin protein and are the smallest of the types
They can easily assemble into filaments and disassemble which makes them very dynamic
Around 7nm in diameter
7
Q
Describe intermediate filaments.
A
They bind intracellular elements together and to the plasmalemma forming a network
They are used in pathology to identify tumours
10-15 mm diameter
8
Q
Describe microtubules
A
Hollow tubules composed of alpha and beta tubular subunits in alternating array
Serves as a “motorway” network of the cell
Originate from the centrosome (MTOC)
They are polar
Important in cilia, flagella and mitotic spindle
9
Q
How do Dynein and kinesin work with microtubules?
A
They attach to the microtubules and move along them, dragging the membranes of organelles and vesticles along them.
Kinesin= ATPase that moves towards the cell periphery
Dynein= ATPase that moves toward the cell centre
10
Q
What are centrioles ?
A
A pair of organelles composed of many specialised microtubule segments
11
Q
Describe the nucleus.
A
Contains genetic code and is the site of RNA synthesis
it is enclosed by a nuclear envelope made of inner and outer nuclear membrane which nuclear pores providing continuity with the cytoplasm
Between the inner and outer nucleus is the PERINUCLEAR CISTERN
mRNA and tRNA are transcribed in the nucleus and rRNA is transcribed in the nucleolus
12
Q
What is EUCHROMATIN?
A
DNA that is more dispersed and actively undergoing transcription.
13
Q
What is HETEROCHROMATIN?
A
DNA that is highly condensed and not undergoing transcription.
14
Q
Describe ribosomes.
A
Formed in the nucleolus
Instrumental in protein synthesis
Each made up of a small subunit which binds to RNA and a large subunit which catalyses the formation of peptide bonds
15
Q
What is the endoplasmic reticulum?
A
Reticulum = net-like structure The endoplasmic reticulum forms a network of interconnecting membrane bound compartments in the cell Two types (RER and SER) Increase in ER = increase in the metabolic activity of the cell
16
Q
Describe rough endoplasmic reticulum.
A
Studded with ribosomes
Plays a vital role in synthesis of proteins destined for insertion into membranes or secretion
17
Q
Describe smooth endoplamic reticulum.
A
Continues the processing of proteins produced in the RER
The site of synthesis on lipids
Most cells contain relatively little SER
18
Q
Describe the Golgi complex (apparatus)
A
It is composed of a group of flattened, membrane bound cisternae (membrane disks) arranged in sub-compartments. Transport vesicles (structure containing liquid) arrive at the Golgi from the SER/RER The Golgi cisterns function in the modification and packaging of macromolecules synthesised in the ER (adds sugar, cleaves protein, sorts macromolecules into vesicles)
19
Q
Describe the mitochondria
A
Oblong cylindrical organelles composed of inner and outer membrane
The inner membrane is extensively folded to form cristae which increases SA
They are the power generators of the cell so function in the generation of ATP (via oxidative phosphorylation and the synthesis of certain lipid and proteins)
Contain their own DNA and system for protein production
Increase in mitochondria in a cell = increase in metabolic rate
20
Q
What are intercellular junctions?
A
Specialised membrane structures which link individual cells together into a functional unit
3 types ; occluding, anchoring and communicating
21
Q
Describe occluding junctions
A
Link cells to form a diffusion barrier ( preventing diffusion)
Appear as a focal region of close together adjacent cell membranes
Also known as TIGHT junctions or ZONULA ADHERENS
22
Q
Describe anchoring junctions
A
Link sub-membrane actin bundled of adjacent cells
Also termed ZONULA ADHERENS
Provide mechanical strength
23
Q
What does a desmosome do?
A
Link sub-membrane intermediate filament or adjacent cells. Very common in the skin where they provide mechanical stability
24
Q
What is a junctions complex
A
Close association of several types of junction found in epithelial tissues
25
Describe communicating junctions
Allow movement of molecules (selective diffusion) between cells
Each junction is a circular patch studded with several hundred pores
Pores are produced by connexon proteins
Found in the epithelia but also in some smooth muscle and cardiac muscle where it is critical for the spread of excitation
26
How can material move across the cell membrane?
eDiffusion
Transport proteins
Vesicular transport (endocytosis and phagocytosis)
27
What is endocytosis?
How material from an extra cellular space can be incorporated into a cell
The cell membrane invaginates, fuses and the newly made endocytotic vesicles buds into the cell. This is often receptor mediated
28
What is phagocytosis?
How bacteria or larger material from extra cellular space is incorporated into the cell
The bacterium bings to the cell surface receptors triggering extensions of the cell to engulf it forming a phagosome
The phagosome binds with a lysosome carrying a digestive enzyme producing a phagolysosome
29
How is tissue preserved?
The tissue must be thinly sliced to allow light to penetrate the tissue
Then it must be impregnated with a support material (usually wax) by dehydrating it, putting it in an organic solvent and placing it in hot wax
Thin sections are then put on a microtome and put on microscope slides, the wax washed off and the tissue rehydrated.
Changes/ distortions from the original tissue are ARTIFACTS
30
What are H&E dyes?
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Haematoxylin = a BASIC dye with the affinity for ACIDIC molecules and stains them purplish blue
Eosin = an ACIDIC dye that’s has an affinity for basic molecules and stains them pinkish red
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31
What are the problems with interpretation of histological techniques?
You are essentially seeing a 3D object in 2D , since a simple bent tube can produced many different shapes when sliced thinly , you can see many different aspects of a tissue
32
What is the epithelium?
The epithelium covers surfaces of the body, lines hollow organs and forms many glands. It occurs as sheets and varies widely in size, shape, orientating and function.
33
What are features of the epithelium?
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The adhesions between epithelial cells is strong and sheets of cells have minimal intercellular space (perfect for surfaces and body cavities)
It has a BASAL LAMINA
They are non-vascular
Cells are usually polarised
It can also form solid organs e.g liver
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34
What are some functions of the epithelia?
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Mechanical barriers (skin)
Chemical barrier (lining of stomach)
Absorption
Secretion
Containment (urea)
Locomotion (cilia)
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35
What are the two types of epithelia?
Covering and glandular
36
How can covering epithelia be classified ?
Cell shape
No. Of layers
Cell surface or tissue specialisations (prominent microvilli,cilia, presence of layers of keratin)
Presence of specialised cell types (goblet cells)
37
How can cell shape be classified?
Squamous (flattened,fish scale)
Cuboidal
Columnar (tall and thin)
38
How can the number of layers be classified?
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Simple = one layer
Stratified = two or more layers
Pseudostratified = appears multilayered but are all connected to the basal lamina
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39
What is a basal lamina?
A layer of extracellular matrix components to which the cells are attached
40
What do endocrine glands do?
Secrete products towards the basal end of the cell and then it is distributed to the vascular system throughout the body
41
What do exocrine glands do?
Secrete products toward the apical end of the cell either into the lumen of an internal cell, into a duct or onto the body surface
42
What are the four types of tissue?
Epithelial
Connective tissue
Muscle
Nervous
43
What are the three types of connective tissue?
Hard connective tissue
Soft connective tissue
Blood and lymph
44
What is connective tissue made of?
Connective tissue consists of extracellular matrix and cells. The types of connective tissue is determined by the types and relative amounts of these two components
45
What are they two types of soft connective tissue?
Loose soft connective tissue = loosely packaged fibres separated by abundant ground substance. Cells are relatively plentiful
Dense soft connective tissue = densely packaged bundles of collagen fibres. (Dense regular = Fibres aligned, dense irregular = fibre bundles run in many directions
46
What are the types of hard connective tissue?
Cartilage and bone
47
Describe cartilage.
Strong, flexible, semi-rigid and compressible tissue.
It is avascular and receives nutrients from adjacent tissue by diffusion through its matrix
There are 3 types (HYALINE, elastic and fibrocartilage
48
Describe bone connective tissue.
It has an outer shell of dense CORTICAL bone which makes up the shaft
CANCELLOUS or TRABECULAR bone occupies the end of the bone, it is a fine network of bone.
It undergoes remodelling throughout life
Bone is a living tissue that is penetrated by small canals for blood vessels and nerves, containing living cells OSTEOCYTES
49
What makes muscle specialised?
The cytoplasm of muscle cells is packed with contractile fibres that are highly specialised for the production of contractile force. Force is produced by actin fibres over myosin fibres with the aid of a number of accessory proteins
50
What are the types of muscle?
Smooth muscle
Skeletal muscle
Cardiac muscle
51
Describe smooth muscle
Also called involuntary or visceral
Structurally simplest of the muscle types
It has no visible striations and is not under conscious control
Mostly found in organs
The individual fibres are elongated, spindle shapes cells with great range in length. They have a cigar shaped nucleus in the centre of each fibre.
52
Describe skeletal muscle
Also called voluntary or striated muscle
The muscles of the body that respond to conscious control
Fibres are usually giant multinucleated, cylindrical cells where the nuclei are elongated and locates at the periphery of the cell.
53
Describe cardiac muscle
Forms the major parts of the walls of the heart chambers and origins of great vessels
It has striations but they are less prominent than skeletal muscle
The fibres are much shorter than skeletal muscle and branch to form a complex network
Single nucleus located at the centre
Intercalated disks are the sites of end to end attachments between adjacent cells.
54
What is nervous tissue made of?
Neurons and Glia (support cells)
| Glia far outweigh the neurons
55
What is the protective coat of the CNS
Meninges
56
What is the protective coat of the PNS
Epineurium
57
What are the three types of neurons?
Multipolar - many dendrites only one axon (most common)
Bipolar - one dendrite, one axon
Pseudopolar - short process gives rise to axons in both directions
58
What are the principle glia of the CNS?
Astrocytes - support ion transport
Oligodenrocytes - produce myelin in brain and spinal cord
Microglia- produce immune surveillance
59
What is the principle glia of the PNS
Schwann cells - produce myelin and support axons
60
What are the 3 major salivary glands?
Parotid, submandibular and sublingual
61
Describe the parotid salivary gland
- epithelium organ
- longest of the glands
- produces more water than the other glands
62
Describe the sublingual gland
This is the shortest duct which produces more mucus than the others.
63
Describe the submandibular gland
50/50 water and mucus and is shorter than the parotid but longer than the sublingual
64
Why are salivary glands striated?
To allow the modification of saliva by pumping out the salt so the fluid is hypotonic to blood.
65
What are the four major layers of the digestive tract?
Mucosa, submucosa (loose connective tissue), muscularis externa (two thick layers of smooth muscle) and adventitia (connective tissue)
66
What are the three parts of the mucosa layer of the digestive tract?
1- epithelium (sits on the basal lamina)
2- lamina propria (loose connective tissue)
3- muscularis mucosae (thin layer of smooth muscle)
67
What are the types of mucosa?
secretory, protective and absorptive
68
What is protective mucosa ?
It has Non- keratinised stratified squamous epithelium (oral cavity, pharynx, oesophagus, Anal canal)
69
What is absorptive mucosa?
Simple columnar epithelium with villi and tubular glands (small intestine)
70
What is secretory mucosa?
Simple columnar epithelium with extensive tubular glands (stomach)
- it produces mucus to protect from acid
71
What is protective and absorptive mucosa?
Simple columnar epithelium with tubular glands (large intestines)
- it dehydrates material
72
What is the enteric nervous system?
= The digestive tracts own nervous system.
It has around the same no. Of neurons as the spinal cord and receives input from the autonomic nervous system to coordinated a gut response locally.
73
What is a ganglia?
A group of neurons (that mostly live between the two muscle layers of the muscularis externa).
74
What are the layers of the trachea?
Respiratory epithelium, lamina propria and the hyaline cartilage of the tracheal ring
75
What’s the difference between bronchi and bronchioles
Bronchi are large diameter airways and have hyaline cartilage in their wall.
Bronchioles are smaller airways, have no cartilage and smooth muscle predominates their wall.
76
Describe the epithelium of alveoli
Alveoli have the thinnest possible epithelium with a simple squamous shape so their is as small as possible distance between the air and blood.
77
Describe the structure of lobules in the liver.
The liver is made up of a large number of lobules each with a similar hexagonal arrangement. At each corner is a branch of the hepatic portal veins and hepatic artery. In the centre is a central vein.
78
How does blood get through the liver lobules?
The hepatic portal vein and hepatic artery deliver the blood to the lobule > the blood passed from the corner to the centre via hepatocytes (epithelial cells which interact with blood) > the central vein drains to the hepatic vein.
79
Describe how the pancreases is both an endocrine and exocrine gland
The exocrine pancreases produces digestive juices to breakdown proteins, lipids, DNA etc
The endocrine pancreas consists of small scattered islands of tissue called Islet of langerhans which produce a number of hormones including insulin.
80
What are the three layers of blood vessels ?
Tunica intima - a single layer of squamous epithelial cells (endothelial cells) with a basal lamina and a thin layer of connective tissue
Tunica media - predominantly smooth muscle, thickness varies
Tunica adventitia - supporting connective tissue
81
How are the layer of blood vessels separated ?
The tunica initima and tunica media are separated by a layer of elastic tissue called the INTERNAL ELASTIC MEMBRANE
The tunica media and tunica adventitia are separated by a layer called the EXTERNAL ELASTIC MEMBRANE
82
In what way is the tunica media of the aorta different to smaller arteries ?
A significant amount of the smooth muscle in the tunica media is replaced by sheets of elastic fibres.
83
What is the vasa vasorum?
In large arteries only the inner part of the wall can obtain nutrient from the lumen , so the vasa vasorum is their own vascular supply
84
What is the difference between arteries and arterioles?
Arterioles have only one or two layers of smooth muscle in their tunica media and almost no adventitia.
85
What are capillaries composed of?
Endothelial cells and a basal lamina
86
What are the three types of capillary?
Continuous (muscle, nerve, lung, skin)
Fenestrated - have small pores (mucosa, endocrine glands, kidneys)
Discontinuous or sinusoidal - have large gaps (liver, spleen, bone marrow)
87
What are venules?
Capillary networks drain into post-capillary venules
They are endothelial cell lines and contain a thin layer of connective tissue (important for gas exchange)
They are vessels with smooth muscle in the tunica media
88
What is the structure of veins?
Veins have a tunica intima, a thin, continuous tunica media (few layers of smooth muscle) and an obvious tunica adventitia.
The largest veins have thick tunica adventitia which has longitudinally oriented smooth muscle
They often have valves
89
What is the lymph vascular system?
A system of relatively thin-walled vessels that drain excess tissue fluid into the blood stream.
Transports lymph to lymph nodes for immunological surveillance.
Smooth muscle in walls
Has Valves
90
Where in the body is the most blood found?
The peripheral veins
91
What are the formed elements? (45% blood volume)
Red blood cells, white blood cells and platelets
92
What are the types of white blood cell?
Granulocytes and agranulocytes
93
What are the types of granulocytes ?
Neurophils, eosinophils and basophils
94
What are the types of agranulocytes?
Lymphocytes and monocytes
95
What is plasma (55% blood volume) made up of?
90% water
Proteins
Nutrients and salts
96
How can blood be separated?
In a centrifuge
| Red blood cells at the bottom, White blood cells in the middle and plasma at the top.
97
What is serum?
Plasma which has had the clotting factors removed
98
Describe erythrocytes.
(Red blood cells) are biconcave disks about 7micrometers
They have no nucleus and 1/3 of their volume is haemoglobin
They contain a network of flexible cytoskeletal elements that allow them to deform and slip through smaller spaces
they last approx. 4 months and are removed by the spleen and liver
99
Rank the proportion of each type of leukocyte from most to least present.
(White blood cells)
| Neutrophils, lymphocytes, eosinophils, monocytes, basophils
100
Describe neutrophils
Their cytoplasm contains many granules but theses stain poorly with acidic or basic dyes
They have a prominent multi-lobed nucleus
They circulate in an inactive state but if stimulated by the presence of bacteria or inflammation they enter the tissue and become phagocytes
Abundant and short lived - a significant portion of bone marrow is devoted to production
101
Describe eosinophils
The prominent granules in the cytoplasm have an affinity for ACIDIC dye.
Cells are released from the marrow and circulate for 8-12 hours then move to the tissues.
They are slightly larger than neutrophils
Typically have a biolobed nucleus
They are important in reducing inflammation in allergic reactions and asthma and fighting parasitic infection
102
Describe basophils
The prominent granules in the cytoplasm have an affinity for BASIC dyes
They have a biolobed nucleus
The granules contain histamine, heparin and other inflammatory mediators
They are effectors in allergic reactions
103
Describe monocytes
They are the precursors of tissue macrophages and together they form the mononuclear phagocyte system
They are found all over the body but mainly in loose connective tissue
Largest cells circulating in the blood and have a non-lobulated nucleus
They have small lysosomal granules
104
Describe lymphocytes
Have a round nucleus surrounded by a thin to moderate layer of cytoplasm without visible granules
Two types B and T which cannot be distinguished in normal stains
Both arise in the bone marrow but T cells differentiate in the thymus
B type gives rise to antibody decreasing plasma cells and T forms a complex set of cells that perform defence functions
105
Describe platelets
They are small cell fragments and play a key role in homeostasis
They have a well developed cytoskeleton which participated in excluding granules and clot retraction.
Have some organelles but no nucleus and conspicuous granules containing coagulation factors.
106
Describe hemopoiesis
=formation of blood components
During the first 3 weeks of gestation the erythrocytes are formed outside the embryo
After this the liver and to some extent the spleen are colonised by hemopoietic stem cells and in the second trimester the liver is the principal site of blood formation.
By birth bone marrow is the main site of blood formation. As bones enlarge there is excess capacity and so hemopoiesis is shut down in many bones.
107
What are the names for mononuclear phagocytic cells in other areas of the body.
Kupffer cells (liver), microglia (brain), langerhan’s cells (skin)
