B2.3 Cell Specialisation Flashcards
What are stem cells
cells that continue to grow and divide repeatedly, rather than specialise
What are morphogens
a small number of genes determine body patterns during the embryo development
They are extracellular and occur across a gradient of concentrations
what do morphogens do
high concentration of morphogens will cause cells to act diff from when there is a low concentration
this means initiation/inhibition of gene expression is a result of different concentrations of morphogens
they control the way cells differentiate and develop in specific tissues
what is a blastocyst
a tiny balls of cells, formed through continual cell division
what are embryonic stem cells
cells found on the inner cell mass of the blastocyst
What are adult stem cells
few cells that keep many of the properties of embryonic stem cells
what does it mean that stems cells are self renewing and have potency
they maintain undifferentiated states and have the capacity to differentiate in mature cell types
what is a stem cell niche
an area of tissue that provides a specific environment where stem cells exist in undifferentiated and self renewable states
They can then receive stimuli to determine their behavior
What can a result of signals in stem cell niches be
maintenance of a dormant state
cause to self renew
commit to a more differentiated state
Bone marrow is ..
the site of blood cell formation for most vertebrates
what is an osteoblast
cells which regulate the creation of bones
what is Hematopoietic Stem Cells
they produce RBC, WBC and platelets
They are closely connected with osteoblasts because they rely on each other to function
What is the vascular niche
in the adult bone marrow, is a place for stem cell mobilisation , proliferation , differentiation
What are hair follicles
they are structures that can regenerate in order to continuously produce new hair
They are multipotent and have the potential to increase rapidly
what happens during the growth phase of hair follicle stem cells
becomes activated to regenerate the hair follicle causing hair to grow longer every day
what happens to hair during the resting phase of hair follicles
the stem cells are dominant and hairs shed more easily
what causes hair to turn white
hair follicles have pigment cells that make melanin
certain stem cells act as pigment producing.
Fewer of these cells become active and hair loses its ability to produce melanin
what can lead to hair loss with age
imbalance in stem cells differentiation and altered stem cell activity
What are totipotent stem cells
the most versatile type, they are the first formed stem cells of a zygote
Can become any type, including cells that make the placenta
what are pluripotent stem cells
slightly limited in potential, can give rise to any cell type that makes up the body, but cannot make placental or totipotent stem cells
when are pluripotent stem cells found
as blastocyst is formed, stem cells in subsequent division are pluripotent
what is multipotent stem cells
stem cells are only able to develop and form the nervous system after differentiation has occurred
can develop into diff cell types but very limited
have limited capacity for self renewal
what is the function of multipotent stem cells
they can create, maintain and repair the cells of one particular organ or tissue
why are egg cells large
the large body allows it to store nutrients for the early development of the fertilised egg
why are sperms tiny
they only need to hold the nucleus for delivery
purpose of the sperms long flagellum
provides propulsion to reach the egg
shape and size of RBC related to it’s function
much smaller than WBC so they can fit through small lumen of capillaries
have large SA compared to volume , allowing oxygen to diffuse at a faster rate
what does WBC do
attack and destroy foreign matter
large size allows them to engulf pathogens or produce antibodies
why are neurons and nerve cells long
allow electrical impulses to be sent without interruption over a long distance
allows fast transmission
what are striated muscle fibres
multinucleated cells attach to muscles to allow movement. their length allows them to coordinate contraction and has an effect on muscle force generation
what factors the rate at which materials can enter or leave the cell
the surface area
what happens to SA and volume as cells increase in size
volume increases faster than the surface area, SA to volume ratio falls
means less and less cytoplasm has access to SA for exchange of materials
what does low SA to volume ratio show in cells
cells cannot constantly grow larger
When limit is reached, the cell may then divide
what are adaptations of RBC to increase SA to volume ratio
they have biconcave shape
flattened to increase SA and diffusion
no nucleus
shape of cell increases its flexibility
what are adaptations of Proximal convoluted tubule to increase SA to volume ratio
walls of tubule are one cell thick and packed with mitochondria
inside surface folded into microvilli, forming brush border ( increase SA)
on other side, invaginations formed to increase surface area
What is Proximal convoluted tubule
the longest section of the nephron,
reabsorbs large amounts of the filtrate
what is an adaptation of an alveolus to maximise gas exchange
wall is one cell thick, right next to capillaries
what are features of Type 1 pneuomocytes
involved in gas exchange between the alveoli and the capillaries
have flattened shape, extremely thin
cells tightly connected to prevent leakage of tissue fluid into alveolar air space
what are features of type 2 pneumocytes
they produce detergent like mixture of lipoproteins and phospholipids known as surfactant which line inner surface of alveoli
cuboidal and big
contain many secretory vesicles
surfactant lowers surface tension so walls dont collapse inwards of alveoli
what are macrophages
they are abundant in the surface film and protect the delicate structure of the alveoli
originate bone marrow stem cells and disperse in the body through blood circulation
they migrate into alveoli where phagocytes ingest foreign stuff
what does myogenic origin mean
when the impulse to contract is generated by the muscle ( found in heart)
what is the structure of heart muscle cells
each cell has a tubular structure composed of chains of fibres
each fibre composed of a mass of myofibrils
what does cardiac muscle consists of
cylindrical branching columns of fibres, allowing for 3d contraction and signal to spread quickly
in cardiac muscle, what is structure of the fiber it is composed of
each fibre has a single nucleus and they have a striated appearance
they are surrounded by a plasma membrane known as the sarcolemma, well supplied with mitochondria and capillaries
what does the structure of cardiac muscle cells allow
propagation of stimuli through the heart wall
what is present at the junction between cardiac muscle cells
intercalated discs, helps synchronise contraction of the muscle
what does an intercalated disc consist of
double membrane with gap junctions, through which there are cytoplasmic connections between adjacent cardiac cells
what do gap junction in cardiac muscle cells allow
continuous flow of cytoplasm between cells
what does the branching structure of the cardiac muscle allow
connection to multiple cells and provides a large SA of contact between cells, allowing them to work together and synchronize activity
why is network system of atria completely separate from ventricles
to ensure a transmission delay of electrical signal
what are skeletal muscles
they attach the moveable parts of skeletons, contractions of these muscles bring about movements. Muscles are attached by tendons and work in antagonistic pairs
what do skeletal muscles consist of
bundles of muscle fibers, each of which consists of mass of myofibrils
what do skeletal muscle fibres consist of
they appear striped so known as striated
each fibre consists of parallel myofibrils, within a sarcolemma
they are multinucleated and contain specialised ER
Sarcolemma folds to form a sarcoplasmic reticulum, network around individual myofibrils
what are similarities between skeletal muscle and cardiac mucle
both surrounded and enclosed by sarcolemma from which transverse tubules are present
Sarcoplasmic reticulum present in both
both striated and similar arrangement of actin and myosin filaments
muscle fibres can shorten
many mitochondria to increase ATP for contraction
what is the advantage of delaying the two divisions of meiosis in egg cells
they’re provided with genetic material for longer, for mRNA production and protein synthesis,
what is the function of follicle cells in egg cell
nourish and protect cell
function of jelly coat/zona pellucida in egg
binding of sperm cells
prevents polyspermy and premature implantation
function of cortical granules in egg
prevents polyspermy
function of plasma membrane in egg cell
surrounds nucleus and contains microvilli for absorption of nutrients
