21-09-21 - Primary Tissues Flashcards
What are tissues?
what does an organ usually contain?
What are the 4 advantages of tissues?
- Tissue is a group of specialised cells with a distinct function
- An organ usually contains a number of tissues grouped together
- The advantage of tissues:
- Division of labour and coordinated function for tissues
- Larger organisms are possible
- Support and motility (capable of motion)
- Exploitation of resources not available to single cells.
What does every cell in the body contain?
What determines cell function and structure?
What does selective expression result in?
What do most differenciated cells have in common?
- Each cell contains the full genome present in the first cell of the embryo (20-25000 protein codes)
- Proteins determine the cell function and structure
- Most cells only express a subset of these genes
- This selective expression and gene silencing results in the differentiation of hundreds of different cell types in the bodies, with varying looks and functions (ex. Regulating transcription or modification of DNA)
- Differentiation produces distinct cells, but most cells contain a similar set of organelles (Nucleus, mitochondria, ER, Golgi, lysosomes, cytoskeletal structure)
Explain how these cells are designed to carry out their function
- pancreatic acinar cells
- muscle cells
- red blood cells
- Pancreatic acinar cell – abundant secretory glands that contain enzymes released for digestion in small intestine.
- Muscle cells – express genes for microfilament contractile proteins actin and myosin in the cytosol
- Red blood cells – Express genes for haemoglobin production then lose all their genes and intracellular organelles, as it is more efficient without them.
What are the different kinds of stem cells?
What are examples of each?
What can they differentiate into?
- Totipotent stem cells – embryonic stem cells within the first couple of divisions after fertilization - Have the ability to develop into a new organism
- Pluripotent – Have the ability to become any cell type in the body
- Multipotent (tissue-specific) – Can differentiate into any cells of the same tissue type
Describe the process of differentiation from the originator cell.
What regulates the gene expression?
- The originator cell undergoes asymmetric division so that the stem cell line continues
- When the originator cell divides, it produces an exact copy and then another copy that has a new set of genes/proteins expressed to produce cells with distinct functions.
- This process continues.
- This gene expression is regulated by transcription factors which act in different combinations in order to determine the path of differentiation
What are the 4 basic types of body tissues?
- Epithelia
- Connective tissues
- Muscle
- Neural tissue
What 5 things can be different in different cell types?
- Cell shape
- Prominent intracellular organelles and cell surface structures
- Binding and association of cells (junctions)
- Arrangement and location of cells
- Extracellular components (extracellular matrix)
What are the 2 types of cilia?
What do they consist of?
=> 9+2
What are they used for?
Where are they found?
- Primary cilium - non-motile (non-motor) – non-moving (also referred to as 9+0)
- Contain 9 microtubule pairs
- Found in many cells
- Can sense movement ex. Liquid flow in kidney tubules.
- Motile cilium (moving) (also referred to as 9+2)
- Contains 9 microtubule pairs on spokes with an inner and out dynein arm. Also contains 2 single microtubules in the centre
- The dynein moves one microtubule pair onto another, which allows the sliding of the microtubules and the movement of the cilium.
- Contains 1 microtubule motor to move it
What are the 7 functions of epithelia?
Where are they found?
What are the different types of epithelium
What are some surface features?
How are epithelial cells connected to eachother?
- Functions: Secretion, absorption, transport, protective barrier, selective barrier, strength and support
- Epithelial tissues covered surfaces in different arrangements
- They are found on top of extracellular matrix material known as the basement membrane
- They can be cuboidal, columnar, squamous, pseudostratified and single (simple) or multiple layers (stratified)
- They can show different surface moderations/ adaptions (cilia and microvilli) that relate to their function
- Epithelial cells are bound to each other by specialised junctions (junction complexes)
What are neurons?
How do they communicate?
What is their function?
what can they be thought of?
- Neurons are separate nerve cells that communicate by releasing chemicals through secretion at the ends of cell processes
- They make up the vast networks of the nervous system
- Can be thought of as an elongated secretory cell
How do neurons communicate at neuromuscular junctions and with one another?
How is this process regulated?
- Signals are collected through the dendrites of the neurons. They are then directed towards the cell
- Axons then direct the stimulus away from the cell towards the axon end bulb into specialised intracellular gaps called synapses.
- The axon end bulb is in very close proximity to the target cell
- Chemical neurotransmitter signals are then released via exocytosis from this axon end bulb towards the target cell. This occurs at the synaptic cleft.
- Complex protein machine regulates vesicle fusion in synapses
How is conduction enhanced in neurons?
What are the cells responsible for this?
how are they formed
And why is this important?
- Oligodendrocytes (myelinating cells) form the myelin for many internodes in the CNS, and Schwann cells (myelinating cells) make myelin for internodes in the PNS (One Schwann cell per internode)
- These internodes are areas in the axon between nodes of Ranvier, and are surrounded by a fatty sheathe made of myelin
- Nodes of Ranvier are periodic gaps in the myelin sheath along the axon
- Both of these enhance conduction and reduces impulse leakage, which increases the rate at which electrical impulses can be passed down the axon.
What do glial cells do?
What are the different glial cells of the CNS and PNS?
- Glial cells are the supporting cast
- They maintain homeostasis, provide myelin, and provide support and protection for neurons.
- Glial cells of CNS - Oligodendrocytes (myelination), astrocytes, microglia, ependyma (lining cells of CNS cavities)
- Glial cells of PNS – Schwann cells (myelination), satellite cells (support cells in ganglia.)
What are astrocytes?
What are the 2 different kinds of astrocytes?
What are the 4 functions of astrocytes?
- Astrocytes (star-cells) are found in both CNS and PNS
- CNS astrocytes are called Protoplasmic astrocytes
- PNS astrocytes are called Fibrous astrocytes
- Astrocytes are responsible for metabolic and mechanical support
- They are present in CNS scar tissue
- They mop up ions for neurons
- They condition the extracellular fluid
What are microglial cells?
What is their function?
- Microglial cells are the resident macrophages (immune cells) of the CNS
- Responsible for phagocytosis and antigen presentation
- Phagocytosis is the cellular process for ingesting and eliminating particles bigger than 0.5µm in size (includes apoptotic cells)
- Can take up foreign substances, break them down in their lysosomes, and present these broken-down components to B-cells to recognise and create antibodies against (antigen presentation)
3 types of muscle tissue:
- Striated or non-striated
- Coordinated or uncoordinated contraction
- Voluntary or involuntary
- Cell description
- Function
- Skeletal muscle
- Striated
- Coordinated contraction
- Direct voluntary (but reflexes can be involuntary)
- Single cells fuse together to form layers
- Work with bones to give body power and strength.
- Cardiac muscle
- Striated
- Coordinated contraction
- Involuntary
- Cells branch and are joined end to end by specialised junction regions called intercalated disks
- Control of blood pump.
- Smooth muscle
- Non-striated (no striking ordered arrays of myosin and actin)
- Coordinated contraction
- Involuntary
- Cells are spindle shaped, but cell borders rarely seen clearly
- Responsible for peristalsis in the gut.
What are the different types of fibrocollagenous network structure? -> type of collagen + amount of cells
Where are they found?
What are the 7 different types of cells in fibrocollagenous tissues?
What do they do?
- Fibroblasts - synthesize fibrous proteins such as collagens, elastin and extracellular matrix components proteoglycans.
- Macrophages -phagocytose foreign bodies/organisms. Present antigens to stimulate immune cells to produce antibodies
- Mast cells - synthesize histamine and other mediators of inflammation.
- Plasma cells - synthesize antibodies (mature B cells (lymphocytes)).
- Stem cells
- Blood cells
- Adipocytes (specialized fat storing cells that accumulate lipids)
What does cartilage do?
What are the different types of cartilage?
Where are they found?
Why does cartilage not appear on normal x-ray pictures?
cartilage ECM + whats inside
- Cartilage brings flexibility, smooth joint movement, strength
- Types of Cartilage:
- Elastic – flexible (elastin++) – in external ear
- Hyaline – impact resistant, durable, low friction – joint surface, trachea
- Fibrocartilage – strong (collagen I++) – intervertebral disks, knee joint menisci
- Cartilage does not lay down substantial amounts of calcium phosphate to be seen as density on a normal x-ray picture.
What is bone for?
What is the structure of bones?
What are the 2 types of bones?
What is the structure in the 2 types of bones?
- Bone is for:
- Skeletal support (force transmission)
- Protection
- Mineral store (calcium)
- Blood cell formation
- Bones are a collagen fibre framework mineralised by hydroxyapatite crystals formed in the matrix
- The two types of bones are:
- Trabecular/cancellous (spongy/porous) – less dense, more open structure than cortical bone
- Cortical (compact bone) – osteocytes arranged in concentric circles around haversian canals
What is white fat adipose tissue for?
Where can it be found?
What does white fast produce?
What did white fat cells form from?
What is the structure of white fat cells like?
- White fat adipose tissue is for energy storage, insulation, protection and support (fat behind eye supports nerves leading in and out of the eye)
- White fat stores produce adipokines that send signals to regulate nutritional balance and other systems (like leptin which signals to the brain that the body has had enough to eat
- White fat cells (adipocytes) form from fibroblast-like precursors
- In a mature fat cell, a single droplet of fat occupies most of the cell, with the nucleus and cytoplasm squeezed to the periphery of the cell
What is brown fat adipose tissue for?
What does it contain?
Who is brown fat particularly useful for?
Where is it found?
- Brown fat makes heat by uncoupling oxidative phosphorylation in mitochondria
- It has a connection to mitochondria, allowing it to burn energy to create heat.
- Contains multiple globules of fat
- Brown fat counters hypothermia in babies, as they have high surface to volume ratio and lose heat easily.
- Brown fat is found in the upper trunk region
Sure!
Brown fat helps generate heat in the body by using a special process that turns energy into warmth instead of storing it as fat. It’s linked to mitochondria, which are like tiny power plants in our cells.
Brown fat has many small fat droplets and is particularly important for babies. Since babies have a high surface area compared to their volume, they lose heat quickly. Brown fat helps keep them warm. You can mainly find brown fat in the upper part of the body, like the chest and neck area.
