Tissue organisation, stem cells, cell differentiation and specialised cells Flashcards
1
Q
What is a stem cell?
A
Unspecialised cells in all multicellular organisms which can undergo cell division and differentiate into (a variety of) specialised cells
2
Q
What are the levels of organisation?
A
Specialised cell -> tissue -> organ -> organ system -> multicellular organism
3
Q
What is a specialised cell?
A
Cells with a specific structure related to a specific function
4
Q
What is a tissue?
A
A collection of similar cells carrying out a specific function
5
Q
What is an organ?
A
A collection of several tissues carrying out the same general function
6
Q
What is an organ system?
A
A group of organs that work together to perform one or several common functions
7
Q
What is potency in stem cells?
A
A stem cell’s ability to differentiate into different cell types
8
Q
What is a totipotent stem cell?
A
- They can differentiate into all cell types of both embryo and placenta
- Produced from the fusion of an egg and sperm cell into a zygote
- A fertilised egg, or zygote and the 8 or 16 cells from its first few mitotic divisions are totipotent cells, which will eventually form a whole organism
- They can also differentiate into extra-embryonic tissues like the amnion or umbilicus
9
Q
What is a pluripotent stem cell?
A
- Can differentiate into any cell/tissue type (found in an embryo) but cannot differentiate into placenta or extra embryonic cell/tissue
- Cannot form whole organisms
- They are present in early embryos and are descendents of totipotent cells, called the blastocyst
They differentiate into three germ layers:
- The endoderm
- The mesoderm
- The ectoderm
10
Q
What is a multipotent stem cell?
A
Can produce cells of closely related tissues (can only form a range of cells with a certain type of tissue) e.g. adult stem cells in the bone marrow differentiate into all blood cells
11
Q
What is a unipotent stem cell?
A
They can produce only one cell type, but have the property of self-renewal (cell division) which distinguished them from non-stem cells e.g. skin cells, cells lining the small intestine, hepatocytes (liver cells)
12
Q
What is the name for stem cells in plants and where are they found?
A
- The meristematic cell, which is totipotent
It is found in many tissue:
- Apical meristem (tips of shoots and roots)
- Lateral buds
- Vascular cambium (forms xylem and phloem)
13
Q
What are the broad categories of human stem cells in research? And what are their potencies?
A
- Adult stem cells: found in adult tissue e.g. bone marrow => multipotent
- Embryonic stem cells: derived from blastocysts (early embryo) and is obtained from IVF treatment => pluripotent
- Foetal stem cells: from amniotic fluid or miscarrige/abortion => multipotent
- Induced pluripotent stem cells (iPS): pluripotent cells generated directly from adult non-stem cells => pluripotent
- Cord blood stem cells: found in the umbilical cord => multipotent
14
Q
What are the ethical issues of using embryonic stem cells?
A
- It involves the destruction/discarsion of human embryos which are a potential life
- The embryo cannot give consent
- There is a debate about when life begins
- There are religious and moral objections to the use of embryos in this way as many believe that life begins at conception and destruction of the embryo is murder
15
Q
What are the ethical issues of using adult stem cells?
A
- Harvesting bone marrow is painful and risky
- Vulnerable, low income populations may be exploited for stem cell donations
16
Q
What are the ethical issues of using cord blood stem cells?
A
- Consent & Ownership: Concerns over informed consent and who owns the stem cells
- Commercialization: Worries about companies profiting and exploiting parents.
- Equity & Access: Limited access due to cost, leading to disparities
- Genetic Engineering: Ethical concerns about editing or cloning using stem cells
- Uncertain Use: Doubts about whether stored cells will ever be needed or used.
- Privacy: Risks of genetic information being accessed or exploited
17
Q
What are the ethical issues of foetal stem cells?
A
- Often obtained from aborted or miscarried fetuses so using them for research raises moral concern
- May be viewed as controversial or insensitive
18
Q
Where do foetal stem cells come from?
A
From amniotic fluid or miscarrige/abortion
19
Q
What are the ethical issues of using induced Pluripotent Stem cells (iPS)?
A
- It is still a fairly new method so could be unethical for use in human treatments before properly ensuing their safety and effectiveness
- Long term effects of the genetic changes are not known
20
Q
What is the technical name for red blood cells?
A
Erythrocytes
21
Q
How are erythrocytes adapted to their function?
A
- Have a flattened biconcave shape which increases their surface area to volume ratio and this is essential to their role of transporting oxygen around the body
- They do not have nuclei or many other organelles which increases the space available for haemoglobin (the molecule that carries oxygen)
- They are flexible so that they are able to squeeze through narrow capillaries
22
Q
What is the technical name for white blood cells?
A
Neutrophil
23
Q
How are neutrophilds adapted to their function?
A
- They have a multilobed nucleus which makes it easier for them to squeeze through small gaps to get to the site of infections
- The granular cytoplasm contains many lysosome that contain hydrolytic enzymes used to attack pathogens
24
Q
What is epithelia? And name some examples?
A
Single or multiple sheets of cells covering outer and inner surfaces of the body and lining cavities of organs, including blood vessels
Examples include:
- Squamous epithelia
- Ciliated epithelia
25
What is the funtion of a sperm cell?
It is a male gamete that delivers genetic information to the female gamete, the ovum (egg)
26
How are sperm cells adapted to their function?
- Sperm have a tail or flagellum, so they are capable of movement and contain many mitochondria to supply the energy needed to swim
- The acrosome on the head of the sperm contains digestive enzymes, which are released to digest the protective layers around the ovum and allow the sperm to penetrate, leading to fertilisation
27
How are palisade cells adapted to their function?
- Contain many chloroplasts to absorb large amounts of light for photosynthesis
- The cells are rectangular box shapes, which can be closely packed to form a continuous layer
- They have thin cells walls, increasing the rate of diffusion of carbon dioxide
- They have a large vacuole to maintain turgor pressure
- Chloroplasts can move within the cytoplasm in order to absorb more light
28
How are root hair cells adapted to their function?
Have long extensions called root hairs which increase the surface area of the cell maximising the uptake of water and minerals from the soil
28
What is the function of guard cells? And where are they found?
- They are on the surface of leaves and form small opening called stomata
- They regulate the rate of transpiration within plant cells by opening and closing the stomata
- These are necessary for carbon dioxide to enter plants for photosynthesis
29
How does a stomata open and close?
- When guard cells lose water and become less swollen as a result of osmotic forces, they change shape and the stoma closes to prevent further water loss from the plant
- The cell wall of a guard cell is thicker on one side so the cell does not change shape symmetrically as its volume changes
29
How are squamous epithelium adapted to their function?
- Sometimes known as pavement epithelium due to its flat appearance
- It is very thin due to the squat or flat cells that make it up and also because it is only one cell thick
30
When is squamous epithelium present? And where is it found?
- It is present when rapid diffusion across a surface is essential
- It forms the lining of the lungs and allows rapid diffusion of oxygen into the blood
31
How are ciliated epithelium adapted to their function?
- Ciliated epithelium lines the trachea, for example, causing mucus to be swept away from the lungs
- Globelet cells are also present in the air
- This prevents the particles, which may be bacteria, from reaching the alveoli once inside the lungs
32
What is cartilage?
- It is a connective tissue found in the outer ear, nose and at the ends of (and between) bones
- It contains fibres of the proteins elastin and collagen
- Cartilage is a firm, flexible conncetive tissue composed of chondrocyte cells embedded in an extracellular matrix
33
What is the function of cartilage?
- Strong, flexible and acts as a shock absorber
- Prevents friction at the end of your bones and prevents them from rubbing together, causing damage
- Many fish have whole skeletons made of cartilage, not bone
34
What are the three types of cartilage?
- Elastic cartilage
- Hyaline cartilage
- Fibrous cartilage
35
Where is elastic cartilage found?
- External ears
- Eustachian tubes (the tube that carries sounds from your external ear into your head)
- Larynx (voice box)
36
Where is hyaline cartilage found?
- Joint surfaces
- Ribs
- Nose
- Larynx (voice box)
- Trachea
37
Where is fibrous cartilage found?
- Intervertebral disk of the spine
- Insertions of ligaments and tendons
38
What is muscle?
A tissue that needs to be able to shorten in length (contract) in order to move bones, which in turn move the different parts of the body
39
What are the different types of muscle tissue?
- Skeletal
- Cardiac
- Smooth
40
Where is skeletal muscle found? And what is its role?
- Found attached to the bone
- It's role is to move your bones
41
Where is cardiac muscle found? And what is its role?
- Found in the walls of the heart
- It's role is to keep the heart pumping blood around the body
42
Where is smooth muscle found? And what is its role?
- Found in the walls of hollow visceral organs (e.g. liver, pancreas, intestines) except the heart
- Its role is to help with digestion and nutrient collection
43
What is the appearence of skeletal muscle?
Contains myofibrils (which appear as dark pink bands on the micrograph) which contain contractile proteins
44
What is the structure of skeletal muscle?
- Each skeletal muscle fibre is a single cylindrical muscle cell
- An individual skeletal muscle may be made up of hundreds or even thousands of muscle fibres bundled together and wrapped in connective tissue covering
45
What is the appearence of cardiac muscle?
- Consists of long fibres that exhibit cross-striations
- It slightly resembles as skeletal muscle
46
What is the structure of cardiac muscle?
Cardiac muscle cells are joined at their ends by intercalated discs to form long fibres
47
What is the appearence of smooth muscle?
It is round in the centre and tapering at each end
48
What is the structure of smooth muscle?
Thick and thin filaments that are not arranged into sarcomeres giving it a non-striated pattern
49
What is the epidermis of a plant?
A single layer of closely packed cells covering the surfaces of plants
50
How is the epidermis adapted to its function?
- It is usually covered by a waxy, waterproof cuticle to reduce water loss
- Stomata, formed by a pair of guard cells that can open and close are present in the epidermis
- They allow carbon dioxide, water vapour, oxyegn, in and out of the cell
51
What is a xylem tissue?
A type of vascular tissue responsible for transport of water and minerals throughout plants
52
How is the xylem tissue adapted to its function?
- The tissue is composed of vessel elements, which are elongated dead cells
- The walls of these cells are strengthened with a waterproof material called lignin which provide structural support for plants
53
What is the phloem tissue?
A type of vascular tissue in plants, responsible for the transport of organic nutriens, particularly sucrose, from leaves and stems where it is made by photosynthesis to all parts of the plant where it is needed
54
How is the phloem tissue adapted to its function?
- It is composed of columns of seive tube cells seperated by perforated walls called seive plates
- Seive tubes are specialised for transport and lack nuclei
- The phloem has companion cells which are necessary components in the translocation of assimilates
