L8 Growth Flashcards
What should be differentially regulated to maintain the correct proportions and to drive morphogenesis?
Tissue growth must be differentially regulated to maintain the correct proportions and to drive morphogenesis.
What are the different types of tissue growth?
- Cell proliferation
- Cell enlargement
- Growth by accretion
What are the four stages of the cell cycle?
- G1 Phase
- S Phase
- G2 Phase
- M Phase(Mitosis and cytokinesis)
What does the cell cycle have to ensure that a cell does not enter mitosis unless needed?
Checkpoints.
Which checkpoint is the important one for development?
The start checkpoint.
How does the mutation of checkpoint genes, such as retinoblastoma (Rb), contribute to uncontrolled cell proliferation in tumors?
Check point genes are often mutated in tumours to enable cell proliferation (eg retinoblastoma, Rb)
Which phases of the cell cycle are irreversibe?
S, G2 and M phase.
Which checkpoints are responsible for making sure everything is in order before mitosis and cytokinesis (cell division)?
G2/M checkpoint and Metaphase to Anaphase transition checkpoints.
Do proportions of our body chaneg throughout growth?
Yes, children have larger head and smaller limbs and those change while growth.
What controls body size centrally?
Hormones
What is GH (Growth Hormone)?
GH is a central regulator that acts primarily on the skeleton to cause an increase in size.
How does growth hormone act on growth through the liver?
- It is absorbed by liver
- IGF1 - Isulin like growth factor is synthesised
- It is circulated to the bone and stimulates growth.
How does growth hormone act on growth directly?
- Local IGF 1 is synthesised directly on the bone.
IGf - Insulin like growth factor
How many negative feedback loops does hormones have to regulate body size?
Three
What is TOR and Hippo pathway?
TOR (Target of Rapamycin) is a protein kinase that acts as a central regulator of cell growth and metabolism
The Hippo pathway is a signaling network that controls organ size by inhibiting cell proliferation and apoptosis
What is genetic ablation?
Genetic ablation is a powerful technique used in biological research to selectively eliminate specific cells or cell types by manipulating their genetic makeup
What does mutations in hippo cause?
Mutations in hippo cause organ hypertrophy.
What is apoptosis?
Apoptosis is the deliberate suicide of an unneeded cell.
It involves careful coordination of the shut down of the cell – followed by engulfment of the remnants by other cells.
What causes apoptosis and when?
Apoptosis is caused by stress such as starvation or excessive DNA damage.
It is used during development to cull unneeded cells.
In adult tissues it is used for homeostasis (eg mammary gland) and health (eg to get rid of infected (viral) or genetically compromised (tumour) cells).
Why would the removal of a kidney lead to an increase in size of the remaining kidney?
Removal of a kidney leads to an increase in size of the remaining kidney, perhaps in response to a rise in the concentration of creatinine in circulation. Creatine is a waste product which signals the need to increase kidney function. The increase is primarily the result of cell enlargement.
What is necrosis?
Necrosis can be caused by injury, infection, cancer, infarction, and inflammation. It is the disorderly, dying-off of cells without any signal to or from the neighbouring cells. Cells just split open and empty their contents into the surrounding tissue.
What is Myostatin?
Myostatin is secreted by muscle. It provides negative feedback on muscle growth. Mutations that affect Myostatin activity cause increased muscle mass.
It reduces myoblast proliferation (thru Rb) and muscle differentiation (thru MyoD).
What happens if you artificially increase bile acid in the liver?
The liver produces and regulates bile acid levels. Artificially increasing bile acid in circulation causes the liver to grow in response. The increase is the result of cell proliferation. This leads to bile levels being reduced by liver absorption.
What drives body growth?
Skeletal growth.
What do most of the skeleton form as in the embryo?
Most of the skeleton forms as a cartilage template in the embryo
What are chondrocytes?
Chondrocytes are the cells that make up cartilage, a specialized type of connective tissue found throughout the body. Chondrocytes are vital for the structural integrity and function of cartilage, which plays a crucial role in supporting and cushioning our bodies.
What do chondrocytes secrete?
They secrete cartilage matrix in the shape of the skeleton.
Explain the formation of bones.
- Over time after chondrocytes secrete cartilage matrix bone is formed on the cartilage matrix by osteoblasts (ossification)
- During ossification the chondrocytes die by apoptosis
3 .Cartilage remains in the joint areas in adults
Osteoblast = bone cell
Chondrocyte = Cartilage cell
How is the bone matrix assayed to view them?
Bone matrix is red when treated with Alizarin Red
Cartilage matrix is blue when treated with Alcian Blue
Chondrocyte = cartilage cell. Osteoblast = bone cell
In long bones what drives postnatal growth?
Chondrocytes
Explain how growth plates contribute to postnatal growth?
Growth plates contain chondrocytes that proliferate, hypertrophy and then die. The remaining cartilage matrix is turned to bone by osteoblasts.
What is cell hypertrophy?
Cell hypertrophy is essentially the increase in the size of cells, which results in an increase in the size of the affected organ or tissue.
What is the difference between male and female growth in fingers?
In the embryo:
High levels of androgens in the ring finger (4D) promote growth - Male.
High levels of estrogens in the ring finger (4D) repress growth - Female.
What is organ hypertrophy?
Organ hypertrophy refers to the enlargement of an organ due to an increase in the size of its individual cells, rather than an increase in the number of cells
What is the difference between apoptosis and necrosis?
Apoptosis is a controlled, “clean” cell death, while necrosis is a damaging, uncontrolled cellular rupture
Sex specific differences
Biologically sanjith is neither
