UACE Biology > Histology > Flashcards

Histology Flashcards

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1
Q

What is Histology?

A

The study of tissues

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2
Q

What is the importance of tissues

A

Increase the efficiency of an organism by division of work

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3
Q

What are the characteristics of cells in a tissue?

A
  • Generally share a similar origin in the embryo
  • They may be of same type or of different type
  • Share a similar function
  • They are physically linked
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4
Q

What is an organ?

A

A number of tissues working together as a functional unit

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5
Q

What is a system?

A

A functional unit of organs

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6
Q

List plant tissues

A
  • Parenchyma
  • Collenchyma
  • Schlerenchyma
  • Xylem
  • Phloem
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7
Q

List animal tissues

A
  • Epithelial tissues
  • Connective tissues
  • Muscle tissues
  • Nervous tissues
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8
Q

What is the most common characteristic of all parenchyma?

A

They are living tissues

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9
Q

Describe the structure of parenchyma

A
  • The cells are living
  • The cells are roughly spherical or elongated
  • The cells have thin cellulose cell walls
  • The cells have a large central vacuole
  • The cytoplasm and nucleus of the cells are peripheral
  • Made up of tightly packed cells
  • The cells have large intercellular spaces
  • It is made up of one type of cell
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10
Q

Give the functions of parenchyma

A

-Provide support to the plant
-Gaseous exchange
-Store food
-Exchange materials eg water, oxygen, carbon dioxide etc
-Allow growth of the plant
-Passage of water and mineral salts

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11
Q

Give the adaptations of the parenchyma to its function

A
  1. The cells have thin, permeable cell walls that allow exchange of mater eg water, mineral salts, glucose, oxygen and carbon dioxide etc
  2. The cells are closely packed giving them mechanical strength which provides support to the plant
  3. The cells have a concentrated central vacuole which is osmotically active thus providing support via turgidity in herbaceous plants
  4. The large central vacuole of the cells provides adequate space for food storage in the plant
  5. The cells have numerous large intercellular spaces making it suitable for gaseous exchange
  6. The parenchyma is made up of unspecialized cells thus it can perform a variety of functions
  7. Parenchyma is made up of living cells which allows growth
  8. The parenchyma are tightly packed which enables them to act as packing tissue in plants
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12
Q

Where is parenchyma tissue found?

A
  • Rays in woods
  • Cortex
  • Packing tissue in xylem and phloem
  • Pith
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13
Q

Describe the structure of the epidermis

A
  • One cell thick
  • Living
  • Cells are elongated
  • Cells are flattened
  • Tightly packed cells
  • Transparent
  • Has a waxy cuticle; a waterproof layer of cutin
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14
Q

What are the functions of the epidermis as a modified parenchyma?

A
  • Protection of the plant from desiccation and infection
  • Allow light to reach the palisade cells for photosynthesis
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15
Q

What name is given to the layer of cells that replaces the epidermis when it wears out?

A

Cork layer/ cork cells

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16
Q

Describe the structure of the guard cells

A
  • Have pores called stoma
  • Contain chloroplasts
  • Occur in pairs
  • Each cell is bean shaped
  • Inner layer is thicker than outer layer
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17
Q

What are the functions of the guard cells as modified parenchyma?

A
  • Control the opening and closing of the stomata
  • Allow gaseous exchange
  • Control transpiration
  • Site for photosynthesis
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18
Q

Where are guard cells found?

A
  • Leaf epidermis
  • Stems especially herbaceous
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19
Q

Describe the structure of hair like extensions

A
  • Unicellular or multicellular
  • May be hooked
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20
Q

What are the functions of the hair like extensions as modified parenchyma?

A
  • Aid in seed dispersal
  • Absorb water and mineral salts for plants
  • Reduce water loss
  • Protection
  • Promote cross pollination
  • Feeding in carnivorous plants
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21
Q

Where are hair like extensions found?

A
  • Roots
  • Climbing plants
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22
Q

Describe the structure of the glandular cells

A
  • May be hair like
  • Have glands
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23
Q

What are the functions of the glandular cells as a modified parenchyma?

A
  • Secretion of sticky substances
  • Secrete enzymes for digestion and absorption of food in insectivorous plants
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24
Q

Where are glandular cells found?

A
  • Insectivorous/ carnivorous plants
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25
Describe the general structure of the mesophyll cells
- Roughly spherical or irregular - Two layers (palisade above and spongy below)
26
Describe the structure of the palisade mesophyll
- Numerous chloroplasts - Tightly packed - Regularly shaped
27
What is the function of the palisade layer in plants?
- Stores starch - Mechanical support
28
Describe the structure of the spongy mesophyll
- Many intercellular spaces - Irregularly shaped cells - Few chloroplasts
29
What is the function of the spongy layer in plant leaves?
- Sites for gaseous exchange
30
Describe the structure of chlorenchyma
- Living - Contain numerous chloroplasts
31
What are the functions of the chlorenchyma?
- Carry out photosynthesis
32
Where are chlorenchyma found?
- Palisade mesophyll - Outer regions of the cortex
33
Describe the structure of the endodermis
- Living - May be elongated and flattened
34
What are the functions of the endodermis?
- Selective barrier to the movement of water and mineral salts between the cortex and xylem in roots - Responsible for geotropic responses in roots - Store starch grains - Suberin maintains one-way flow of water from the roots to the stem
35
Where is the endodermis found?
- Most conspicuously in roots - Innermost layer of the cortex
36
Describe the structure of the pericycle
- Living
37
What are the functions of the pericycle?
- Produces lateral roots - Contributes to secondary growth
38
Where is the pericycle found?
- Only in roots
39
Describe the structure of companion cells
- Living - Have numerous mitochondria - Living - Elongated and narrow - Small vacuoles - Dense cytoplasm - Adjacent to sieve tubes
40
What are the functions of the companion cells?
- Load food into the phloem
41
Where are companion cells found?
- Adjacent to sieve tubes
42
Describe the structure of collenchyma
- Living - Cell walls are unevenly thickened with cellulose - End walls tapper - Elongated cells - Polygonal shaped cells - Tightly packed cells - Large central cell vacuoles
43
What are the functions of the collenchyma cells?
- Provides mechanical support
44
Where are collenchyma cells found?
- Outer regions of the cortex - Young plants (herbaceous)
45
Describe the structure of sclerenchyma
- Mature cells are dead - Empty lumen - Lignified - Uniformly thickened walls - Interlocking cells - Consist of fibres and sclereids
46
Describe the structure of fibres as sclerenchyma
- Elongated - Lignified - Have pits - Tapering interlocking cells - Polygonal shaped - Form strands
47
Describe the structure of sclereids
- Roughly spherical - Narrow lumen
48
What are the functions of the sclerenchyma?
- Support
49
Describe the structure of xylem
- Made up of parenchyma, tracheids, vessels, fibres - Elongated cells - Cells are joined end to end - Cells are dead - Tubes are hollow/ tubular - Lignified - Bordered pits - Narrow lumen
50
State the functions of xylem
- Conduct water and mineral salts - Provide support
51
What is the use of a torus in conifers?
- Controls entry and exit of water between the cells
52
Describe the structure of tracheids
- Arranged in rows with overlapping ends - Elongated cells - Empty lumen - Cells are dead - Tubes are hollow/ tubular - Lignified - Bordered pits - Narrow lumen
53
Describe the structure of vessels
- Long and tubular - Empty lumen - Lignified - Perforated - End walls are broken down - Cylindrical shape
54
Describe the structure of fibres (sclerenchyma)
- Shorter - Narrow - Thicker walls - Pits - Overlapping end walls - Dead
55
Describe the structure of phloem
- Living cells - Elongated - Tubular SIEVE TUBES - Narrow - Have strands of cytoplasm - Mature sieve tubes lack a nucleus - Elongated - Sieve pores at their end walls - Have sieve plates COMPANION CELLS - Dense cytoplasm - Thin cellulose cell walls - Metabolically active - Numerous mitochondria - Small vacuoles - Elongated - Narrow - Adjacent to sieve tubes - Numerous plasmodesmata
56
State the functions of phloem
- Transport of food throughout the plant
57
Give the similarities between the xylem and phloem
- Both are conducting tissue - Both are elongated - Both exist as parenchyma - Both are perforated - Both exist as fibres - Both are tubular
58
Give the differences between xylem and phloem
XYLEM - Conducts water and mineral salts - Consist of mostly lignified - Movement is from the roots upwards to the rest of the plant - Cells are dead when mature - Does not require energy to transport materials PHLOEM - Transports organic material - Cells are not lignified - Movement is from the leaves throughout the plant - Cells are alive when mature - Requires energy to transport materials
59
What are meristematic tissues?
Group of cells that retain the ability to divide by mitosis
60
Where are meristematic tissues located?
Apical growing points of plants
61
Describe the structure of meristematic tissues
- Small cells - Thin walled - Undifferentiated plastids - Living
62
What is the function of meristematic tissues?
Lead to primary and secondary growth of the plant
63
Describe the structure of epithelial tissue
- Arranged in single or multi layered sheets - Rest on a basement membrane - Some are thick and keratinized
64
Give the general functions of epithelial tissue
- Protection - Reception of stimuli - Absorption - Secretion - Excretion
65
Describe the structure of squamous epithelia
- One cell thick - Rest on a basement membrane - Flattened cells - Nucleus bulges - Centrally placed nucleus - Edges of the cells are irregular
66
Where are squamous epithelia located?
- Alveoli of the lungs - Blood capillaries (called the endothelium here) - Renal capsules
67
Give functions of squamous epithelia
- Permit diffusion of materials - Passage of fluids through hollow structures
68
Describe the structure of cuboidal epithelia
- One cell thick - Rest on a basement membrane - Roughly cube-shaped - Centrally placed nucleus - Free surface may be highly folded into microvilli
69
Where are cuboidal epithelia located?
- Lining of ducts - Lining of proximal and distal convoluted tubules and collecting ducts of kidney - Sweat glands - Thyroid glands
70
Give functions of cuboidal epithelia
Aid secretion (but they are non-secretory as they do not have glands)
71
Which is the least specialized of all epithelia?
Cuboidal epithelia
72
Describe the structure of columnar epithelia
- One cell thick - Rest on a basement membrane - Cells are columnar - Basal nucleus - Have goblet cells
73
Where are columnar epithelia located?
- Stomach lining - Intestinal lining - Lining of the kidney ducts - Thyroid gland
74
Give functions of columnar epithelia
- Secretion - Absorption - Protection - Lubrication
75
Describe the structure of ciliated epithelia
- One cell thick - Rest on a basement membrane - Columnar in shape - Associated with goblet cells
76
Where are ciliated epithelia located?
- Lining of the oviducts - Ventricles of the brain - Spinal canal - Respiratory passages - Body of paramecia - Underside of flatworms
77
Give functions of ciliated epithelia
- Secretion - Movement - Locomotion - Trap dust in the nose
78
Describe the structure of pseudo stratified epithelia
- One cell thick - Rest on a basement membrane - Have false layers - Have goblet cells - Nuclei are at different levels
79
Where are pseudo stratified epithelia located?
- Urinary tract - Respiratory passages
80
Give functions of pseudo stratified epithelia
- Prevent escape of urine - Trap dust and foreign bodies
81
Describe the structure of glandular epithelia
- One cell thick - Rest on a basement membrane - Have goblet cells - Folded
82
Where are glandular epithelia located?
- Lining of intestine - Glands
83
Give functions of glandular epithelia
- Secretion - Lubrication
84
Simple saccular glands would be found where?
Mucus gland in the skin of amphibia like frogs
85
Simple tubular glands would be found where?
Crypts of Leiberkühn in the wall of the small intestines
86
Coiled tubular glands would be found where?
Sweat glands in the skin of humans
87
Simple branched tubular glands would be found where?
Brunner’s glands in the small intestine Gastric glands in the wall of the stomach
88
Simple branched saccular glands would be found where?
Sebaceous glands in mammals
89
Compound tubular glands would be found where?
Salivary glands
90
Compound saccular glands would be found where?
Part of the pancreas that secretes digestive enzymes Mammary glands
91
What is a gland?
A group of cells modified to synthesize and release secretions
92
Define endocrine glands and state an example.
These are ductless glands that release secretions directly into blood Examples; Pituitary gland, Ovary, Testes
93
Define exocrine glands and state an example.
These are glands that have a duct Examples; Sweat glands, Tear glands, Mammary glands, Pancreatic glands
94
Describe merocrine secretion and give examples of glands that make use of it.
- Secretory products are made - Packaged in vesicles - Move to the free surface - Fuse with cell membrane and release secretions by exocytosis Examples include; mucus glands, sweat glands, salivary glands, pancreas
95
Describe apocrine secretion and give examples of glands that make use of it.
- Secretory products are made - Accumulate near the free surface - Secretory parts and parts of the cell break away or pinch off Examples include; mammary glands
96
Describe holocrine secretion and give examples of glands that make use of it.
- Secretory products are made - Accumulate - Secretory parts burst and release its contents Examples include; sebaceous gland
97
Describe the structure of stratified epithelia
- Number of layers of cells - Rest on a basement membrane - Has a germinal layer - Thicker than simple epithelia - First formed cells are cuboid shaped - Cells become flattened as they are pushed towards the free surface (squames) - May be keratinized
98
Where are stratified epithelia located?
- Oesophagus (stratified squamous) - Mammary gland ducts (Stratified columnar) - External skin surfaces - Lining of the mouth - Vagina (cornified) - Sweat gland ducts (Stratified cuboidal) - Bladder (stratified transitional)
99
Give functions of stratified epithelia
- Protection from mechanical damage - Protection against abrasion
100
Describe the structure of transitional epithelia
- 3-4 of layers of cells - Rest on a basement membrane - Has a germinal layer - Thick - Cells are of similar size and shape - Cells are more flattened at the free surface
101
Where are transitional epithelia located?
- Bladder - Ureter - Pelvic region of the kidney
102
Give functions of transitional epithelia
- Prevention of escape of urine - Allow organs stretch prevent them from rupturing
103
Give differences between stratified epithelia and transitional epithelia
STRATIFIED - May be cornified - Has a germinal layer TRANSITIONAL - Not cornified - Does not have a germinal layer
104
Describe the structure of areolar tissue
- Have a jelly- like matrix - Matrix is made of glycoproteins - Have four cells; mast, fat, macrophage, fibroblasts - Cells are widely spread - Macrophage are large and amoeboid shaped - Fibroblasts are large, long and flat - Mast cells have a centrally located nucleus - Have collagen and elastin fibres - Elastin is highly branched - Elastin is elastic - Collagen occurs in bundles - Collagen is unbranched - Collagen is non-elastic
105
What is the use of mast cells?
Secrete an anticoagulant that prevents clotting of blood
106
What do fibroblasts in areolar tissue do?
Produce collagen and elastin fibres
107
What does the ground substance in areolar tissue do?
This is where the fibres and cells are embedded
108
What do macrophages in areolar tissue do?
Defends the body against disease
109
What do fat cells in areolar tissue do?
Stores fat
110
Where is areolar tissue found?
- Between adjacent tissues - Beneath the skin - Connecting organs together
111
Give functions of areolar tissue
- Packing tissue/ supporting tissue - Binds organs and tissues together - [Functions of individual cells]
112
Describe the structure of the two types of fibrous connective tissue
WHITE FIBROUS TISSUE - Has collagen bundles - Has glycoprotein matrix - High tensile strength - Flexible but inelastic - Non-living - Forms a triple helix - Chains are interlinked by hydrogen bonds YELLOW ELASTIC TISSUE - Has elastin fibres - Elastic - Has a glycoprotein matrix - Non-living
113
Where is white fibrous tissue found?
- Tendons - Ligaments - Outer surface of the eye
114
Where is yellow elastic tissue found?
- Walls of arteries - Alveoli of lungs - Ligaments
115
What are the functions of fibrous tissue?
GENERAL - Bind bones together - Bind bones to muscles WHITE FIBROUS - Bring about movement - Allows flexibility YELLOW ELASTIC - Allow stretching of organs
116
Describe the structure of adipose tissue (fatty tissue)
- Cells have a single large fat droplet - Peripheral cytoplasm and nucleus - Cells are closely packed
117
Where is adipose tissue found?
- Dermis of the skin - Around the kidney - Around the heart
118
Give functions of adipose tissue
- Acts as an energy store - Insulation against heat loss - Shock absorber
119
Give the functions of skeletal tissue
- support - Rigid framework for the body - Formation of blood cells - Movement - Attachment site for muscles - Protect internal organs
120
Describe the structure of cartilage
- Hard - Flexible - Matrix is compressible - Matrix is elastic - Chondrin matrix - Chondroblasts embedded in the matrix - They secrete the chondrin - Has collagen - Chondroblasts enclosed in spaces called lacunae become chondrocytes
121
Give functions of cartilage
- Connective tissue - Absorbs mechanical shocks - Resists tension - Reduces friction between bones - Allows flexibility
122
Describe the structure that is unique to hyaline cartilage
- Semi-transparent matrix - Chondrocytes near periphery are flattened - Chondrocytes situated internally are angular - Shiny or glassy
123
Where is hyaline cartilage found?
- Respiratory system - Skeleton of cartilaginous fish - Embryonic skeleton - End of bones and nose
124
What is the function of hyaline cartilage?
- Keeps open the air passages of the respiratory system - Forms the skeleton of cartilaginous fish - Forms embryonic skeleton
125
Describe the structure that is unique to yellow elastic cartilage
- Semi-opaque matrix - Matrix contains a network of yellow elastic fibers - More elastic than hyaline cartilage - More flexible than hyaline cartilage
126
Where is yellow elastic cartilage found?
- External ear - Epiglottis - Pharynx
127
What is the function of yellow elastic cartilage?
- Confer elasticity and flexibility
128
Describe the structure that is unique to white fibrous cartilage
- Bundles of white collagen fibres embedded in the matrix
129
Where is white fibrous cartilage found?
- Intervertebral discs - Symphysis pubis - Ligaments
130
What is the function of hyaline cartilage?
- Joins bones together - Cushioning effect between vertebrae - Provide tensile strength
131
Describe the structure of bones
- Has calcified matrix - Matrix is called the osteum - Hard - Tough - Contains osteoblasts and osteocytes - Osteoblasts are contained in lacunae - Fine canals connect lacunae to each other - Possess blood vessels
132
What is the function of bones?
- Support - Protection of internal organs - Movement and locomotion - Attachment sites for muscles
133
Describe the structure that is unique to compact/ dense bone
- Matrix has collagen fibres - Matrix has salts - Cells called osteoblasts - Tough and compact - Consists of osteons - Consists of numerous cylinder surrounding the canal - Each cylinder is made up of layers called lamellae which are cylindrical - Numerous lacunae between the lamellae - Many fine channels called canaliculi radiate from each lacuna
134
What is the function of compact bone?
- Support - Firm base for tendon insertions - Attachment of muscles
135
Describe the structure that is unique to spongy bone
- Light - Soft - Few inorganic materials - Consists of a meshwork of trabaculae - Collagen fibers
136
What is the function of spongy bone?
- Support - Withstand compression forces
137
State the differences between compact bone and spongy bone
COMPACT - Tough and hard - Lack trabaculae - Have haversian canals - Have periosteum - Have lamellae - Have more inorganic material SPONGY - Light and soft - Have trabaculae - Lack haversian canals - Lack periosteum - Lack lamellae - Have less inorganic material
138
What are the similarities of compact and spongy bone?
- Both contain collagen fibres - Both have osteoblasts
139
What are the differences between cartilage and bone?
CARTILAGE - Flexible - Have chondroblasts - Compressible - Has no blood vessels - Has no bone marrow BONE - Rigid - Have osteoblasts - Incompressible - Has blood vessels - Has bone marrow
140
State similarities between bone and cartilage
- Have lacunae - Contain collagen fibres - Both are hard - Both have a matrix - Both have dormant cells
141
Give the general structure of muscle tissue
- Made up of muscle fibres - Has actin and myosin filaments - Blood supply is adjustable - Dense capillary network - Elastic
142
What are the types of muscle tissue?
- Striated/Voluntary/ Skeletal muscle - Unstriated/ Involuntary/ Smooth muscle - Cardiac muscle
143
Describe the structure of unstriated/ smooth muscle
- Cells have a single nucleus - Fatigue slowly - Unbranched cells - Cells are unstriated/ unstriped - Its action is involuntary - Smooth - Cells are tapered at the end
144
Where may unstriated muscle tissue be found?
- Walls of the iris - Uterine lining - Blood vessels - Lungs - Gut and bladder
145
What are the functions of unstriated muscle?
- Expulsion of the foetus from the uterus during parturition (birth) - Protection of the eye by blinking - Removal of wastes - Regulate gas exchange - Mix and move food in the gut - Alter blood pressure by contracting and relaxing
146
Describe the structure of cardiac muscle
- Cells have one or two nuclei - Does not fatigue - They are striated - Its action is involuntary - Many large mitochondria - Have intercalated discs - Have blood vessels - Contain actin and myosin
147
Where may cardiac muscle be found?
Only in the heart
148
What are the functions of cardiac muscles?
- Aids contraction of the heart for pumping blood
149
Describe the structure of striated/ skeletal muscle
- Cells have numerous nuclei - Bundles of muscle fibre parallel to each other - Muscle fibres are long and cylindrical - Occur in pairs and are antagonistic - Elastic - Connected to motor neurons - Have actin and myosin filaments - Unbranched fibres - Its action is voluntary - Numerous mitochondria - Elongated
150
Where may striated muscle tissue be found?
- Limbs
151
What are the functions of striated muscle?
- Movement - They are effectors and respond to stimuli - Have sarcoplasmic reticulum which is a reserve for calcium ions
152
Describe the ratchet mechanism/ sliding filament mechanism
- Arrival of an impulse - Release of calcium ions from the T-system - Calcium ions bind with troponin - Troponin dislodges tropomyosin exposing the myosin binding site - The myosin head attaches to the binding site - Using energy, myosin pulls actin - Myosin head detaches from the binding site and attaches on a new binding site and pulls again - The cycle is repeated until the muscle contracts - Calcium ions are actively pumped back into the T-system by calcium pumps - Tropomyosin closes up the binding site hence the muscle relaxes
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