Histology Flashcards
1
Q
Define histology
A
The study of microscopic structures and tissues
2
Q
Why is a high resolution needed?
A
To observe and discriminate between cell and tissue components
3
Q
What are the 6 steps in tissue processing?
A
Fixation, embedding, sectioning, mounting, de-waxing, staining
4
Q
What is the process of fixation?
A
Preserves and fixes specimens in place with crosslinks using formaldehyde
5
Q
What is the process of embedding?
A
First dehydrate and remove water with alcohol, then clearing using organic solvent, then replacing with wax (58) or resin (60) for physical support
6
Q
What is the process to sectioning?
A
Sectioned by a microtome to allow discrimination
7
Q
What is mounting?
A
Mounting is the process of mounting tissues to a glass slide to be stained and viewed
8
Q
What is de-waxing?
A
The removal of wax or resin to allow staining using organic solvent, then alcohol and then water
9
Q
Why is staining needed?
A
to show and distinguish specific features.
10
Q
What colour are the nucleus and cellular proteins with H and E stain?
A
DNA/RNA- purple/blue. Intra/extracellular proteins- red
11
Q
What colour does trichrome stain the nuclei, intracellular and extracellular proteins?
A
Nuclei varies, intracellular proteins- red/pink, extracellular proteins- blue/green
12
Q
What are both ordinary CT and cartilage made from?
A
Cells and extra cellular matrix
13
Q
What is ordinary CT used for?
A
Binding muscle to bone and binding individual cells, and allows O2 to diffuse through extra cellular matrix and WBCs
14
Q
What cells in ordinary CT secrete ECM?
A
Fibroblasts
15
Q
What are mature and dormant fibroblasts called?
A
Fibrocytes
16
Q
What features does a fibroblast cell have?
A
Prominent nucleus and granular cytoplasm
17
Q
What is an adipocyte?
A
Fat cell
18
Q
What are the two types of adipocytes?
A
White or brown
19
Q
What are the functions of adipocytes?
A
Energy reserves- triglycerides, thermal insulation, shock absorber- spine, hooves, brown fat for rapid heat producer
20
Q
What causes the pigment of brown fat?
A
The dense mitochondria to rapidly break down the fat and release heat
21
Q
What type of fibres are in the ECM?
A
Collagen, Reticular, Elastic
22
Q
What colour do collagen fibres stain with H&E and trichrome?
A
H&E- pink, Trichrome- Blue
23
Q
Which fibre in ordinary CT is made from abundant proteins assembled into fibres?
A
Collagen- strong and give tensile strength
24
Q
What doe reticular fibres form in the liver?
A
The internal skeleton
25
Which fibre in ordinary CT can recoil?
Elastic
26
Which fibre is needed to limit the stretching of elastic fibres?
Collagen fibres
27
What are proteoglycans in the ground substance made from?
GAGs or hydrated sugars attached to a protein core
28
What are the types of loose connective tissue?
Areolar, adipose and reticular
29
What are the types of dense connective tissue?
dense regular, dense irregular, elastic
30
What are the three types of cartilage?
hyaline, fibro and elastic
31
Why are collagen fibres not usually seen in the ECM?
They have the same refractive properties as ground substance and elastic fibres
32
In cartilage what are the matrix producing cells?
Chondroblasts
33
In cartilage what are chondrocytes found in?
In a semi-solid gell in lacunae, as they shrink during fixation
34
Where are chondroblasts found?
On the surface of the cartilage in the perichondrium
35
What is the main component of cartilage EMC?
Hydrated gel
36
How does cartilage maintain its turgor?
Hydrated gel creates the stiffness and collagen fibres prevent over hydration
37
How do nutrients pass through to cells in cartilage?
Nutrients pass through the hydrated gel as the matrix is avascular.
38
What are the two ways cartilage grows?
appositional and interstitial.
39
What is appositional growth in cartilage?
Growing from the surface by laying down cartilage on the surface (perichondrium)
40
What is interstitial growth in cartilage?
Growth from within the matrix
41
Describe the composition of hyaline cartilage
Mainly hydrated gel, some collagen and little elastic fibres giving a smooth glossy appearance
42
Where is hyaline cartilage found?
Articular surfaces, respiratory tract
43
Describe the composition of fibrocartilage
High amounts of collagen giving high tensile strength
44
Where is fibrocartilage found?
Intervertebral disks
45
What is elastic cartilage high in?
Elastic fibres
46
Where is elastic cartilage found?
Outer part of the ear (pinna)
47
What are two example of liquid support tissue?
Blood and Lymph
48
What is the ECM in blood?
Plasma
49
What is the basal lamina formed from?
The basal lamina is formed from a thin layer of glycoproteins in the ECM which attach to the collagen and muscle, nerve cells as they bind to the receptors on those cells
50
Describe the functional anatomy of the adult bone
Articular layer of cartilage, periosteum surrounding outside and endoosteum lining inside, proximal and distal epiphysis filled with spongy bone, central medullary cavity filled with yellow bone marrow, surrounded by compact bone
51
What is the function of red bone marrow in young animals?
To produce blood cells
52
What is the function of an osteoblast?
Forms bone matrix
53
What is the function of an osteocyte?
Maintains bone tissue
54
What does an osteogenic cell develop into?
Osteoblast
55
What does an osteoclast cell do?
Functions in reabsorption (decalcification)
56
How does an osteoclast break up the matrix?
Attach to the bone surface, release acid to dissolve inorganic matrix, release enzymes to break up organic matrix
57
What is a Haversian system?
Haversian system or and osteon is 3-5 layers of calcified extracellular matrix filled with osteocytes surrounding an individual blood supply which passed nutrients to osteocytes using channels called Canaliculi
58
Describe the cartilage model of developing long bones
Calcified cartilage in the primary ossification centre is broken down by osteoclasts, towards epiphyses, forming medullary cavity, osteoblasts lay down bone on top, secondary ossification centre forms and where it meets from the growth plate
59
List the functions of the components of blood
RBCs- erythrocytes, transport O2, WBCs- leukocytes destroy microorganisms, Platelets- clot blood, Plasma- carries nutrients/hormones and regulates oncotic pressure
60
What process forms blood cell components?
Haemopoiesis in red bone marrow
61
How are red blood cells formed?
Red blood cells begin blue, produce haemoglobin and removes nucleus to become a reticulocyte and mature
62
How are platelets produced?
Platelets are derrived from fragmentation of a megakaryocytic from its cytoplasmic extensions
63
How are O2 and CO2 transported?
O2 binds and from oxyhemoglobin, CO2 can also bind or form bicarbonate
64
Describe the appearence of RBCs in different animals
Dogs- largest, Goats smallest, Cat/Horses similar, Camels/Alpacas oval
65
How can you identify a neutrophil?
Neutrophils have visible pink granules
66
How can you identify a lymphocyte?
Large nucleus, little cytoplasm
67
How can you distinguish a monocyte to a lymphocyte?
Monocytes are larger and has an irregular c-shaped nucleus
68
How can you identify a eosinophil?
They contain pink/orange granules and have a bilobed nucleus
69
How can you identify a basophil?
Contain lavender granules
70
Which of the WBCs are agranular?
Lymphocytes and monocytes
71
What kind of lymphocyte is responsible for cell-mediated immunity?
T-lymphocytes
72
What are B-lymphocytes responsible for?
Humoral immunity
73
Where do both T and B cells stem from?
Stem cell differentiation on bone marrow
74
Where does T-cell and B-cell maturation occur?
T- Thymus and B- Bone marrow
75
What is the connective tissue and the cellular areas in lymphoid organs called?
CT- Stroma, Cellular- Parenchyma
76
What surrounds the thymus?
Connective tissue capsule
77
What is contained in the internal framework of epithelial cells in the thymus?
Macrophages, immature T-cells and mature T-cells
78
What does the medulla of the thymus contain?
Hassall's Corpuscles- thought to destroy self T-cells?
79
What divides the cortex of the thymus?
Septa invaginations divide cortex into lobes
80
Why does the thymus lose its role in adulthood?
T-cells are capable of dividing
81
After maturation where to T-cells go?
They enter post capillary venules in the medulla and leave the thymus
82
Name a primary and secondary lymphoid organ
Primary- thymus, Secondary- Lymph nodes
83
What acts as a filter for lymph?
Lymph nodes
84
What surrounds the lymph nodes, the thymus and spleens?
A connective tissue capsule
85
What forms the internal structure of lymph nodes?
Reticular fibres
86
What do reticular fibres provide a framework for?
To support B-cell and T-cells
87
How does the lymph reach the lymph nodes?
Via many afferent lymphatic vessels
88
After entering the lymph node what route does lymph take?
Starting through the tissue, into sinuses beneath the capsule then into sinuses located around trabeculae (extensions of the capsule)
89
How is lymph drained out of lymph nodes?
Efferent lymphatic vessels
90
Where are nodules in lymph nodes located?
The cortex
91
What do nodules contain in lymph nodes?
Densely packed lymphocytes
92
How are lymphocytes in the inner medulla arranged in lymph nodes?
Arranged in strands called medullary cords separated by medullary sinuses
93
Where do B-cell and T-cells congregate in the lymph node?
B-cells- Cortex, T-cells- junction of cortex and medulla( paracortical zone)
94
What happens when a B-cell becomes activated?
Becomes large and pale, with pale nuclei before dividing to produce plasma and memory cells, in germinal centres, plasma cells leave node
95
What happens when a T-cell becomes activated?
Divide in the paracortical zone, without germinal centres, daughter cells leave node
96
Why do lymph nodes become swollen?
Sinuses are filled with newly formed lymphocytes
97
What does the spleen filter?
The blood
98
What internal framework does a spleen have?
Reticular fibres
99
How is the internal structure separated?
Red and White pulp
100
How does blood enter the spleen?
Trabecular arteries
101
What extends into the spleen to give support?
Trabeculae
102
How is red pulp formed?
Once blood enters the spleen branches of very permeable capillaries cause all of the blood to leave
103
What are RBCs trapped by in the spleen?
Trabeculae
104
What happens to the plasma after filtration in the spleen?
Plasma flows into the venous sinuses and returned to circulation
105
What can red pulp be used for?
It can be squeezed into circulation after sudden blood loss
106
What are PALs?
Periarterial lymphatic sheaths which surround the arteries entering the spleen
107
What arteries do PALS surround?
Central arteries
108
What happens to PALs when blood-borne antigens enter the spleen?
Stimulates B-cells to from pale germinal centres, pushing the arteries to one side and T-cells form darker marginal zones around the germinal centres
109
What do macrophages in the spleen do?
Phagocytose antigens, Debra and ageing erythrocytes
110
What forms the white pulp?
PALs
111
What is lymphoid tissue?
Loose aggregations of lymphocytes in connective tissue, not encapsulated
112
What are the two types of lymphoid tissues?
Permanent e.g tonsils and transient where area is infected
113
What is the process of muscle formation called?
myogenesis
114
What are the function of satellite cells?
A population of inactive myoblasts, for regeneration
115
What are the two myofilaments?
Actin and myosin
116
What encloses a skeletal muscle fibre?
sarcolemma and endomysium
117
What is a fascicle in skeletal muscle?
a bundled group of parallel fibres
118
What covers the fascicles?
Perimysium
119
What surrounds the groups of fascicles in skeletal muscle?
Epimysium
120
Is skeletal muscle striated or unstriated?
Striated
121
What is the dark stained band in skeletal muscle called?
A Band
122
What is the lightly stained band in a skeletal muscle cross section called?
I Band
123
What do 2 Z lines show?
The length of the sarcomere
124
What is the H-band
The darker region of the A band
125
What is the structure of actin?
Two strands attached end to end twisted around each other
126
What other proteins are found in the actin fibres?
Tropomyosin and troponin
127
How is the myosin binding site exposed?
Ca2+ ions bind to troponin and cause tropomyosin to move
128
What is the structure of myosin?
Myosin molecules are arranged back to back each with two heads
129
What is the endoplasmic reticulum in a muscle cell called?
Sarcoplasmic reticulum
130
What is the cell membrane called in a muscle cell?
Sarcolemma
131
What are the specialised invaginations of the sarcolemma called?
T-tubules
132
What is the function of t-tubules?
To carry depolarisation into a muscle cell to the terminal cisternae
133
What are the terminal cisternae?
Sac like regions of the sarcoplasmic reticulum which store calcium
134
What is the difference between association of terminal cisternae and sarcoplasmic reticulum in cardiac and skeletal?
Skeletal- 2 terminal 1 t-tubule (triad), Cardiac- 1 terminal cisternae 1 t-tubule (diad)
135
What is the function of a motor unit in a skeletal muscle cell?
Motor units allow for selective contraction, for the strength go contraction
136
What are myoblasts produced from?
Mesenchymal cells differentiate myoblasts
137
How does hypertrophy occur?
A satellite cell divides into 2 daughter cells, 1 forms a new satellite cell, 1 fuses with myocyte and adds additional nuclei and causes more synthesis of additional myofibrils
138
How is muscle repaired with little damage?
Fusion of satellite cells to form new muscles or to existing muscle cells
139
What happens if damage to a muscle cell is extensive?
Muscle is replaced by scar tissue
140
Where is cardiac muscle found?
Heart and the wall of great vessels
141
How do T-tubules allow for longer contractions of cardiac muscle?
The t-tubules in cardiac muscle are more developed and and release more Ca2+ ions to maintain contractions
142
How are cardiac muscle cells joined together?
Intercalated disks
143
Why are intercalated disks low in electrical resistance?
To allow impulse to travel rapidly
144
Is cardiac muscle striated?
Yes
145
Why do cardiac muscle cells have more mitochondria?
More aerobic respiration takes place
146
What are the functions of purkinje fibres?
The cardio-myocyrtes conduct cardiac potentials more quickly and efficiently
147
Is smooth muscle striated?
No
148
Where is smooth muscle generally found?
Organ systems (small intestine wall)
149
Describe the shape of a smooth muscle cell
Spindle-shaped
150
Where is the nucelus placed in a smooth muscle cell?
Centrally
151
What does smooth muscle lack that other types have?
No t-tubule system with little sarcoplasmic reticulum
152
What is the definition of a gland?
A group of cells with the main or only function is the synthesis and secretion of material with extracellular function
153
What are examples of things gland secrete?
Proteins (enzymes), glycoproteins (mucus), steroids, lipids
154
What are the two classes of glands based on function?
Apical secretion and Basal secretion
155
What is apical secretion?
Glands that secrete their contents onto free epithelial surface and are classified as exocrine glands- deprived from epithelial layer and retain connection via draining duct
156
What is basal secretion?
Glands that secrete their contents into underlying connective tissue, which pas into tissue fluid or blood- endocrine glands.
157
What are the two embryological origins of endocrine glands?
Epithelial, Neuronal- morphology retained e.g hypothalamus/posterior pituitary- endocrine e.g adrenal medulla
158
What are the 2 classes of exocrine glands classed based on shape?
Simple and Compound
159
How does a simple exocrine gland drain?
They drain directly with or without a duct onto epithelia surface e.g sweat gland
160
How does a compound gland drain?
Consists of a branching system, ducts from many secretory units join together to form one large duct
161
How are exocrine glands classed based on secretion and morphology
Exocrine glands are either mucous or serous (mucous or protein)
162
What hormones does the thyroid gland produce?
T3 and T4 responsible for regulating metabolism
163
How does the thyroid make sure to never run out of hormones T3 and 4?
It synthesises and stores thyrogloblin (TGB) which is broken down by phagocytosis when required
164
What are the adrenal medulla and cortex responsible for?
Medulla- derived of sympathetic neurones which secrete adrenaline. Cortex- synthesis and release hormones.
165
What does the epithelium do?
Cover and line internal and external surfaces of the body
166
How is the epithelium separated from underlying tissues?
Basal lamina
167
What are the two main types of epithelia?
Simple and stratified
168
What are the 4 types of simple epithelia?
Squamous- flattened, Cuboidal- cuboidal, Columnar- rectangle, Pseudostratified columnar- fake
169
What is the function of simple squamous?
Rapid transport and low friction
170
What is the function of simple columnar?
Absorption, secretion, moving material
171
What are the types of stratified epithelia?
Stratified squamous, keratinised stratified squamous, parakeratotic stratified squamous
