Cells & Tissues Flashcards
How can we break the body down in a hierarchical manner?
- Cells - 100’s of different types - grouped together to perform specific function
- 4 different categories of tissue –> tissue organise together to perform a specific task
- Organs have different types of tissue to perform inter-related functions - e.g. heart receive and pump blood around the body
- Body-systems collection of organs coming together - digestive tract
What does the circulatory system consist of? What is its most basic function?
Circulatory system
Heart + blood vessels + lymph vessels
Function - allows circulation of substances throughout the body - delivery and removal of substances/molecules throughout the body
What does the respiratory system consist of? What function does it play?
Structures - Lungs (including surrounding structures), oral and nasal cavity
Function - Allows us to breathe - central for gas exchange
What does the nervous system consist of? What function does it play?
Consists of the central and periphery nervous system
Role - Communication via electrical signals
What does the digestive system consist of? What function does it play?
Consists of the mouth, esophagus, stomach, small intestine, large intestine, and anus - hollow organs
But also consists of the solid organs - liver, pancreas, and gallbladder
Role - Digestion (breakdown), absorption of nutrients and excretion of waste products.
What does the urinary system consist of? What function does it play?
Consists of the kidneys, ureters, urinary bladder, and urethra.
Function - filtration of blood and release of waste
What does the musculoskeletal system consist of? What function does it play?
Musculoskeletal system - bones, muscles, tendons, ligaments and soft tissues
Muscles - Produce force to create movement - voluntary and involuntary
Skeletal - create structure, shape the body, provide protection, store minerals and make blood cells
What does the immune and lymphatic system consist of? What function does it play?
Immune - White blood cells, antibodies, complement system, etc.
Lymphatic - main sites - lymph vessels, bone marrow, spleen, thymus gland, lymph nodes, and the tonsils
Function (together) - protective system of the body/fights of pathogens/invaders
What does the endocrine system consist of? What function does it play?
Endocrine - consists of a range of organs that produce hormones and target tissues where hormones act on.
Function - Form of communication - chemical signalling
What does the reproductive system consist of? What function does it play?
Reproductive system
Male - Penis, testicles, scrotum, prostate, vas deferens and urethra
Female - ovaries, uterus, vagina, and vulva
Function - Responsible for sexual reproduction but also in hormone production.
What does the integumentary system consist of? What function does it play?
Integumentary system - epidermis, dermis, hypodermis, associated glands, hair, and nails
Function - Physical barrier, temperature regulation, cell fluid maintenance, detection of stimuli and vitamin D synthesis
What is the estimated number of cell in the body? What is the predominant cell type?
Estimate - 3 x 10^13 cells
Red blood cells make up to 84% of the number of cells in your body.
Following that we platelets make up the second largest group - 4.9%
This means that only 11% of cells are nucleated
Even though the skin is the largest organ it only makes up less than 1% of the total number of cells
What at the different components that make up the standard eukaryotic cell?
The cell is the smallest functional unit of the body
Difference between the cytosol and the cytoplasm?
Cytosol - refers to the watery fluid that fills up the cell
Cytoplasm - refers to the entire content within the cell membrane (excluding the nucleus)
What is the plasma membrane? What is its function? What are its principal components?
Plasma membrane - outer layer of the cell that encloses the cytosol within it
Function - protection, separates the cell from the rest of its environment, controls the entry and exit of substances into the cell – acts as a barrier
Principal components - phospholipids (form a bi-layer - hydrophilic head and hydrophobic tail), cholesterol, channel proteins, sugar chains,
What are organelles? What are some examples?
Organelles have a unique and highly specialised function within the cell
Examples…
Nucleus
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Mitochondria
Golgi apparatus
Ribosomes
Centrioles
Lysosomes
What is the nucleus and what are its functions?
Nucleus - site of DNA storage and transcription
Largest organelle, surrounded by a nuclear envelope
Contains the genetic material of the cell (DNA) in the form of chromosomes
Contains a structure - nucleolus - involved in the synthesis of ribosomes
In an H&E stain what colour does the nucleus and cytoplasm appear?
Nucleus - Purple
Cytoplasm - Pink
What is the cytoskeleton? What are its different components? What role does it play?
The cytoskeleton is a network of protein fibres that give the cell shape and allow it to move
Different components
1. Microfilaments (actin) - Small fibres that provide structural support and allow contractions
2. Microtubules (tubulin) - Larger fibres also involved in movement and transport
3. Centrosome - directs organisation of microtubules. Composed of a pair of centrioles. Important in cell division
4. Cell extension - Projections of the plasma membrane and Important for movement
Explain what the following diagram is showing.
Actin filaments allowing for cellular movement
1. Cells creates lamellipodia
2. Filopodia stick out with adhesive protein at the end
3. Leading edge adheres whereas trailing end is not
4. Forward movement
What is the mitochondria and what is its function?
Mitochondria are often described as the ‘powerhouse’ of the cell - bean shaped organelle with double membrane that is highly folded.
Function - Produce energy for the cell through aerobic respiration
What are the functions of the two endoplasmic reticulum’s?
Smooth
- Responsible for synthesising lipids and steroid hormones
- Drug detoxification
Rough
- Studded with ribosomes
- Responsible for protein synthesis to be exported from the cell –> proteins that are packaged in a vesicle to be released or embedded into the cell membrane
What are ribosome and what role do they play?
Ribosomes are small granules that are made up of RNA and protein
Function - protein production centre of the cell - translation - convert mRNA into protein
Can be found in the cytoplasm and on the RER
- Cytoplasmic ribosomes make proteins for use in the cell
- RER ribosomes make proteins for export
What is the Golgi and what role do they play?
Golgi apparatus is a stack of membrane-bound sacs (cisternae)
Function - Important for export of proteins from the cell. Also plays an important role in producing lysosomes and glycosylation of protein’s
What are the average/range of sizes of the cell, nucleus, mitochondria and lysosome?
Definition of a tissue? What are the four different groups/categories?
Tissues are large groups of similar cells grouped together to perform a particular function.
Tissues are classified according to the size, shape and function of their constituent cells.
What is the Extracellular matrix (ECM)?
Complex structural entity surrounding and supporting cells that are found within mammalian tissues and it is often referred to as the connective tissue –> view it as scaffolding
All tissues are composed of CELLS and EXTRACELLULAR MATRIX (ECM) - made by cells and exported to the extracellular space
Consists of macromolecules (e.g. protein) and minerals
Where is epithelial tissue found? What function does this tissue type play? WHat are the two main categories?
Covers the body, lines body cavities and found in glands
Structure is closely related to functions of…
1. Protection
2. Secretion
3. Absorption
Epithelial tissue can be
SIMPLE – a single layer of cells
STRATIFIED – multiple cell layers
What is squamous simple epithelial tissue?
Simple Squamous Epithelium
Flattened cells attached to a basement membrane
Lines the heart, blood vessels, lymph vessels, lung alveoli and collecting ducts of the kidney nephron
What is a simple cuboidal epithelium?
Simple Cuboidal Epithelium
Cube-shaped cells attached to a basement membrane
Forms kidney tubules and some glands
Important role in secretion, absorption and/or excretion
What is a simple columnar epithelium?
Simple Columnar Epithelium
Rectangular-shaped cells attached to a basement membrane
Found in stomach, small intestine, trachea, fallopian tubes
Can be ciliated
What are the two types of stratified squamous epithelium?
- Keratinised stratified epithelium
- Found at Dry surfaces –> Skin, hair and nails
- Top layer of cells have no nuclei and contain keratin - this forms water proof layer – forms dry layer - Non-Keratinised stratified epithelium
- Moist surfaces, protects them from drying out
- Mouth, pharynx, oesophagus and vagina
What is a pseudostratified epithelium?
Pseudostratified Epithelium
Gives the impression of multiple cell layers but each cell is attached to a basement membrane –> in reality it is a simple epithelium
Pseudostratified columnar ciliated epithelium is only found within the respiratory tract - “Mucociliary escalator”
What are examples of different types of connective tissue?
Describe the features of loose (areolar) connective tissue
Note don’t confuse with lungs…
Most abundant connective tissue type
Semi-solid matrix of collagen and elastin fibres containing fibroblasts, adipocytes, mast cells and macrophages
Connects and supports other tissues
Eg. Under skin, between muscles
Describe the features of adipose tissue.
Areolar tissue matrix containing adipocytes
Adipocytes contain large fat globules
2 types
- White adipose tissue
About 20-25% BMI in normal, healthy adults
Acts as a thermal insulator and energy store - Brown adipose tissue
Found in the new-born
Highly vascularised
Describe the features of reticular connective tissue?
Found in lymph nodes and organs of the lymphatic system
Matrix consists of reticular fibres
Cells present are reticular cells and white blood cells
Describe the features of dense connective tissue & what are the two main types?
Low cell numbers but high in fibre content
Can be FIBROUS TISSUE or ELASTIC TISSUE
- Fibrous tissue
Collagen fibres in closely-packed bundles
Fibroblast cells sit between fibres
Eg. Tendon, ligament, periosteum (covering bones) - Elastic tissue
Elastin fibres secreted by fibroblast cells
Tissue has high degree of recoil
Found in organs where change of shape is common
Eg. Blood vessels, lungs
Describe the features of cartilagenous connective tissue - what are the three main types?
Consists of chondrocytes (cartilage cells) embedded in a collagen and proteoglycan matrix
Three types of cartilage in the body
- Hyaline – ends of long bones (articulating cartilage) – reduce friction and shock absorption
- Fibrocartilage – intervertebral discs
- Elastic fibrocartilage – outer ear
What do these micrscope image show?
Describe the features of bone (connective tissue)
Specialized type of connective tissue - consists of bone cells (osteocytes) embedded within a mineralised collagen matrix (collagen + minerals)
Two types of bone…
1. Compact bone located on the outside of the bone shaft
2. Spongy/cancellous bone located internally
Osteoblasts – lay down new bone matrix
Osteoclasts – remove bone matrix
Osteocytes – mature bone cells that reside within the matrix
Describes the features of skeletal muscle.
Skeletal muscle
- Striated (striped), multinucleated muscle fibres
- Under voluntary control
- Moves bones of the skeleton
What is an important thing to keep in mind when looking at microanatomy images?
Image taken from different directions - impact the view in the final image
Describe the features of smooth muscle tissue.
Smooth muscle
- Non-striated
- Under involuntary control
- Useful in propelling contents along tubes by peristalsis (rhythmic contractions)
- Found in gut tube, ureter etc.
- Cells are mononucleated
Describe the features of cardiac muscle tissue.
Cardiac muscle
- Striated
- Under involuntary control
- Mononucleated
- Cardiac muscle makes up the walls of the heart
- Intercalated discs between cells help propagate wave of contraction
- Branching on cells
Summarise the type of nucleation, appearance and control of the three muscle types.
What are occluding junctions?
Occluding junctions - tightjunctions
Main role is to seal cells together to prevent molecules from leaking either to another cell or across a boundary
What is the role of anchoring junctions? What are the different types?
Main role is to mechanically attach cells (and their cytoskeletons) to adjacent cells or to theextracellular matrix.
What role do communicating junctions play? What are the two types?
Main role is to control the passage of signals (chemical or electrical) from one cell to the other.
Most cells are linked to their neighbors via gap junctions
Connexins are the channel forming proteins
Good examples are cardiac and smooth muscle cells
What is the process used to visualize a tissue under a micrscope?
Technique known as histology
Tissue is sliced into thin sections and stained
- Tissue Biopsy
- Fixation - 4% formaldehyde
- Processing - reduce the water content
- Embedding - embed in wax (replace water with wax) – wax block
- Sectioning - thin ribbons from wax block
- Staining - differentiate cells, tissues, organelles, etc.
- Visualization
What are the different stains used in histology?
H&E - most common
Haematoxylin & Eosin (pink - cystoplasm & purple - nuclei)
Masson’s Trichrome
Connective tissue stain (green – connective tissue, red and black - nuclei)
Von kossa
Mineral stain (black - bone)
Alizarin red
Mineral stain (red – bone)
Oil red O
Fat globule stain (red)
