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( ) ( :النحل العمر أرذل إلى يرد من ٧٠ومنكم) () ( هود شيخا بعلي وهذا عجوز وأنا أألد ويلتا يا قالت تعالى قوله

1-Understand the multidimensional approach to the practice of geriatric medicine.

2-Become familiar with biology of aging

3-Appreciate the different theories of aging process.

Geriatrics is a subspecialty of medicine that focuses on health care of the elderly.

The term geriatrics differs from “Gerontology” which is the study of the aging process itself. The term comes from the Greek geron meaning "old man" . However "Geriatrics" is considered by some as "Medical Gerontology".

Aging:

A process of gradual and spontaneous change, resulting in maturation through childhood, puberty, and adulthood and then decline through middle and late age.

Senescence: The process by which the capacity for cell division, growth,

and function is lost over time, ultimately leading to an incompatibility with life; i.e., the process of senescence terminates in death.

Although aging has both the positive component of development and the negative component of decline, senescence refers only to the degenerative processes that ultimately make continued life impossible.

Normal aging:

Refers to the common complex of diseases and impairments that characterize many of the elderly.

However, persons age very differently: some acquire diseases and impairments, and others seem to escape specific diseases altogether and are said to have died of old age.

Successful (healthy) aging:

Refers to a process by which deleterious effects are minimized, preserving function until senescence makes continued life impossible. Persons who age successfully avoid experiencing many of the unwanted features of aging.

Young- old: From the age of 65 to 75 years old.Adult-old : From the age of 75 to 85 years old.Oldest- old: older than 85 years old.

Ageing is not an 'intrinsic' process, as it occurs in the

context of an organism's interaction with the environment.

Although genes play a part in ageing, a major contributor

lies in the build-up of random damage, left unrepaired by

inefficient somatic cellular 'housekeeping' mechanisms.

1-Oxidative stress This occurs when the production of reactive oxygen

species )free radicals( exceeds available antioxidant systems.

Interaction of these free radicals with DNA in mitochondria and the nucleus leads to mutations and deletions, especially in the mitochondria where DNA repair mechanisms are less efficient.

This process continues until oxidative phosphorylation is compromised, adenosine triphosphate )ATP( production declines and cells begin to die.

2-Protein modification by glycation Advanced glycosylation )enzymatic process that links

saccharides to produce glycans, attached to protein,lipids or other organic molecules( end-products are produced by spontaneous reactions between protein and local sugar molecules, a process which is increased by oxidative stress.

These products damage the structure and function of the affected protein, which becomes resistant to breakdown. This is the cause of the yellowing of ageing nails and cornea.

3-Cell Senescence : - This is a further important phenomenon. - Fibroblasts )A type of cell found in connective tissue

produces collagen( divide only until they are dense enough to contact each other-a phenomenon called contact inhibition.

-If diluted, the fibroblasts divide again until maximum density is reached. They can only undergo a limited number of cell divisions )the Hayflick limit(.

Leonard Hayflick in 1965 discovered the Hayflick limit during research, which was an observation that cells dividing in cell culture divided about 50 times before dying..

The Hayflick limit varies amongst different cell types, their physiological age, and more so from organism to organism.

As cells approach this limit, they show more signs of old age )enters a senescence phase( presumably because the telomeres )A telomere is a region of repetitive DNA at the end of a chromosome keep the ends of the various chromosomes in the cell from accidentally becoming attached to each other. (, reach a critical length.

This suggests a 'biological clock' capable of counting the number of cell divisions, with the possible function of preventing cancer.

The site of the 'clock' is thought to be in the telomere end regions of DNA, which shorten with each cell division.

adenine )A(, thymine )T(, cytosine )C( and guanine )G(.

N.B. Single-stranded non-circular DNA molecule has two non-identical ends, the 3' end and the 5' end )usually pronounced "three prime end" and "five prime end"(.

The numbers refer to the numbering of carbon atoms in the deoxyribose, which is a sugar forming an important part of the backbone of the DNA molecule.

In the backbone of DNA the 5' carbon of one deoxyribose is linked to the 3' carbon of another by a phosphate group.

Telomere FunctionTelomeres are repetitive DNA sequences )"telomeric DNA"(

and associated proteins that cap the ends of chromosomes )"capping" proteins( .

Telomeres have several roles:

-They protect chromosome ends from degradation and fusion.

- They allow complete chromosome replication.

- They position the chromosomes within the nucleus.When telomeres are sufficiently eroded, cells stop dividing.

Patients with the premature ageing Werner's syndrome display damaged DNA due to lack of a helicase (An enzyme that is capable of unwinding the deoxyribonucleic acid double helix at a replication(, which is required for DNA repair and messenger RNA formation, and demonstrate particularly shortened telomeres.

4-Weak link theory: This theory posits that a specific physiologic system--

usually the neuroendocrine or immune system--is particularly vulnerable.

Failure of the weak system accelerates dysfunction of the whole organism.

Failure of the neuroendocrine system would be expected to produce profound impairments in homeostatic systems, including loss of reproductive function and metabolic regulation, which occur with age.

Failure of the immune system would be expected to produce an increased susceptibility to infection and a decreased ability to reject tumor cells.