CELLULAR ADAPTATIONLecture 4

CELLULAR ADAPTATIONLecture 4

Adapted

Cell

+StressNormal

cell

Stress = ?

Increased/decreased workload

* skeletal muscle and body building

* cardiac muscle and hypertension

* skeletal muscle disuse (limb immobilization)

Increased/decreased stimulation

* estrogenic stimulation of uterus in pregnancy

* estrogen/prolactin stimulation of breast (lactation)

* denervation of muscle

- Stress

Adapted

Cell

Cellular adaptations to stress

1. Hyperplasia (more cells)

2. Hypertrophy (bigger cells)

3. Atrophy (smaller cells)

4. Metaplasia (different types of cells)

3. Atrophy (smaller cells)

1. Physiologic

During development: i.e. notochord; thyroglossal duct

2. Pathologic (local or generalized) via

* disuse * Loss of endocrine stimulation

* denervation * Aging

* ischemia * Pressure

* Nutrition

Atrophy(Mechanism)

Reduction in structural components

Decreased number of mito, myofilaments, ER via

proteolysis (lysosomal proteases; ubiquitin-

proteosome system)

Increase in number of autophagic vacuoles

Residual bodies (i.e. lipofuscin brown atrophy)

NB: diminished function but not dead

ATROPHY-THYMUS GLANDATROPHY-THYMUS GLAND

ATROPHY-LIVERATROPHY-LIVER

CORTICAL ATROPHY

Normal Artophied

Brain atrophy

Muscle fiber atrophy. The number of cells is the same as before the

atrophy occurred, but the size of some fibers is reduced. This is a

response to injury by "downsizing" to conserve the cell. In this case,

innervation of the small fibers in the center was lost. This is a trichrome

stain.

DISUSE ATROPHY(Poliomyelitis)

DISUSE ATROPHY(Poliomyelitis)

ATROPHY in OSTEOPOROSISATROPHY in OSTEOPOROSIS

HYPOPLASIA-GAS INSUFFICIENCY

HYPOPLASIA-GAS INSUFFICIENCY

HyperplasiaHyperplasia((more cells)more cells)

1. 1. PhysiologicPhysiologic

* Hormonal (breast/uterus in pregnancy)

* Compensatory (liver after partial hepatectomy)

2. Pathologic2. Pathologic

Excessive hormone/GF stimulation of target

tissue

* Endometrial hyperplasia (x’s estrogen)

* Benign prostatic hyperplasia (x’s androgens)

* Connective tissue cells in wound healing

HyperplasiaHyperplasia(Mechanism)

Cell proliferation

via increased production of TRANSCRIPTION FACTORS

due to

* Increased production of GF

* Increased levels of GF receptors

* Activation of intracellular signaling

Results in larger organ

HYPERPLASIA-PROSTATE GLANDHYPERPLASIA-PROSTATE GLAND

Thyroid hyperplasia

HYPERPLASIA-UTERUSHYPERPLASIA-UTERUS

Adapted

Cell

2. Hypertrophy (larger cells)

* Not due to swelling

* Increased synthesis of structural

components

* Results in larger organ

* May occur with hyperplasia

HYPERTROPHY OF SMOOTH MUSCLE IN ASTHMA

HYPERTROPHY OF SMOOTH MUSCLE IN ASTHMA

CARDIAC HYPERTROPHYCARDIAC HYPERTROPHY

Myocardial hypertrophy. - Cross-section of the heart of a patient with long-standing hypertension - Shows pronounced, concentric left ventricularhypertrophy

Hypertrophy (Heart)

Question

Which term is most likely to fit the description of the uterus during pregnancy?

A. hyperplasia

B. hypertrophy

C. aplasia

D. dysplasia

E. metaplasia

Metaplasia(Mechanism)

Reprogramming

1. of stem cells present in normal tissues

2. of undifferentiated mesenchymal cells in connective tissue

Mediated by signals from

cytokines, Growth Factor

Leading to induction of specific transcription factors

METAPLASIA-ESOPHAGUSMETAPLASIA-ESOPHAGUS

4. Metaplasia **One adult cell type replaces another**

Reversible

Columnar to squamous epithelium (most common epithelial -type of

metaplasia)

Chronic irritation i.e. (in trachea and bronchi of smokers)

Vit A deficiency squamous metaplasia in respiratory epithelium

May be some loss of function

May predispose to maligancy

Photomicrograph of the junction of normal epithelium

(1) with hyperplastic transitional epithelium (2).

Photomicrograph of the trachea from a smoker. Note that the columnar

ciliated epithelium has been replaced by squamous epithelium.

METAPLASIA-LUNGSMETAPLASIA-LUNGS

DYSPLASIA-LeftDYSPLASIA-Left

• Cellular dysplasia refers to an alteration in the size, shape and organization of the cellular components of a tissue.

• It is established that dysplasia is a preneoplastic lesion, in the sence that, it is a necessary stage in the multi-step cellular evolution to cancer.

DYSPLASIADYSPLASIA

DYSPLASIA-CERVIXDYSPLASIA-CERVIX

Question Which of the following best describes the

phenomenon of epithelial dysplasia? A. an increase in thickness of the epithelium because of increased number of cells B. a decrease in thickness of the epithelium owing to decrease in the number of dividing cells C. an irregular proliferation and maturation of cells throughout the layers of the epithelium D. an increase in the thickness of the epithelium owing to enlargement of the component cells E. absence of epithelium because of lack of cell proliferation

MUSCULAR DYSTROPHYMUSCULAR DYSTROPHY

Muscular Dystrophy

• What Is Muscular Dystrophy?Muscular dystrophy is a disease in which the muscles of the body get weaker and weaker and slowly stop working because of a lack of a certain protein (see the relationship to genetics?)

• Can be passed on by one or both parents, depending on the form of MD (therefore is autosomal dominant and recessive)

ANAPLASIAANAPLASIA

• Next Meeting:

• Study Inflammation and Repair