Cell Growth and Adaptation

What is the goal of cell adaptation?

To maintain homeostasis

What are some factors that influence cell growth?

Cell microenvironment

Physical or mechanical stressors on tissues

Genetic alterations of cells

How does the cell microenvironment impact cell growth and adaptation?

Growth factors

ECM

Abnormal or inappropriate cell stimuli

Nutrients

What is aplasia?

Cells do not grow

Characterized by absence or partial absence of a tissue or organ

All aplasia are caused by what?

Genetic defect

What is hypoplasia?

Decreased growth of cells

Why does hypoplasia look like?

Developmental problem leading to incomplete or partial formation of a tissue or organ

What causes hypoplasia?

Congenital morphological abnormalities

What is atrophy?

A decrease in cell size or cell number

What is hypertrophy?

Increase in cell size

What is hyperplasia?

Increase in cell number

What is physiological hyperplasia?

Cells increase in number to fulfill their functional responsibilities (normal)

What are some examples of physiological hyperplasia?

Endometrial hyperplasia during pregnancy

Fibroblast hyperplasia during healing

Mammary glandular hyperplasia during lactation

GI epithelial hyperplasia to replace excessive mucosal loss

What is pathological hyperplasia?

Increased cell numbers and activity are detrimental to the animal

What are some examples of pathological hyperplasia?

Excessive fibroblast proliferation during healing

Bone loss secondary to parathyroid hyperplasia

Thyroid hyperplasia causin tracheal compression

What is physiological hypertrophy?

Cells increase in size to fulfill their functional responsibilities

What are some physiological hypertrophy examples?

Uterine smooth muscle hypertrophy during pregnancy

Cardiac myocyte hypertrophy during training

Skeletal muscle hypertrophy due to increased demands

What is pathological hypertrophy?

Usually excessive physiological hypertrophy

What are some examples of pathological hypertrophy?

Cardiac myocyte hypertrophy in a failing heart

Small intestine muscular hypertrophy causing intestinal stenosis

Hypertrophy as a primary change is restricted to what cells?

Muscle cells

How do myocytes respond to increased demand?

Increasing in size, not by number

T/F myocytes are post-mitotic cells that don’t undergo replication?

True

Why do hyperplasia and hypertrophy occur concurrently usually?

Increased demand for function by most cell types is met by both increased size and increased number of cells

What are some examples of hyperplasia and hypertrophy being linked?

Endocrine: parathyroid hyperplasia and hypertrophy

Mucosa: Intestinal crypt hyperplasia and hypertrophy

Parenchyma: Prostatic hyperplasia and hypertrophy

What is physiological atrophy?

Atrophy occurring in response to decreased demand for the function of the cell

What are some examples of physiological atrophy?

Endometrial and myometrial atrophy following parturition

Mammary glandular atrophy at the end of lactation

Myocyte atrophy due to decreased activity or training

What is pathological atrophy?

Inappropriate loss of stimuli or inhibitory stimuli result in atrophy

What are some examples of pathological atrophy?

Skeletal muscle atrophy following dennervation

Bone loss due to mineral imbalance (occurs with renal failure)

Loss of stimulation of endocrine tissues

What is metaplasia?

There is replacement of one mature cell type with another mature cell type

What is the most common metaplasia?

Cuboidal to squamous

What is a physiological metaplasia?

Physiologic metaplasia often a response to irritation or an adverse environment

Very rare

What are some examples of physiological metaplasia?

Squamous metaplasia of salivary and esophygeal ducts/lands due to vitamin A deficiency in birds

Squamous metaplasia of airway mucosa due to poor air quality/chronic infection

What are some examples of pathological metaplasia?

Decreased pulmonary defense

Decreased glandular secretions

Osseous changes in various tissues

What is dysplasia?

Abnormal cell morphology and growth

What is different about cells that have dysplasia?

Size, shape and appearance are different

Larger nuclei, more organelles, more rapid mitosis

What can cause dysplasia?

Chronic irritation or infection

Can be a pre-neoplastic change

What is dysplasia at a tissue/organ level?

Congenital or acquired gross abnormalities characterized by abnormal tissue or organ morphology

What are some examples of dysplasia at the tissue/organ level?

Chondrodysplasia

Retinal dysplasia

Hip dysplasia

What is anaplasia?

Cells are poorly differentaited

Describe what a cell with anaplasia looks like

Lack of morphologic features of the cell they were derived from

Nuclei and other cell structures have abnormal morpholoy

Anaplasia is seen in what type of cells?

neoplastic cells

What is neoplasia?

A new growth of genetically abnormal cells

What does the cell morphology of neoplastic cells look like?

Pleomorphic

T/F neoplastic cells have all undergone a mutation?

True