Cell Life Cycle, Mitosis, and Skin Structure: A Comprehensive Biology Review

Mitosis

Cell division of the somatic (body) cells resulting in two identical daughter cells.

Cell division

Replacing cells and generating new cells, important for growth and repair.

Growth

The process where a single cell develops into a multicellular organism.

Repair

The process of replacing old or damaged cells with the same type of cell.

Cytokinesis

Division of the cytoplasm in a cell.

Chromatin

Unwound DNA in non-dividing cells.

Chromatids

Two identical chromatin threads held together at a centromere.

Chromosomes

Tightly coiled DNA strands visible during mitosis.

Interphase

The longest phase of cell division where the cell grows and prepares for division.

G1 (growth 1)

Initial growth stage of interphase.

S (synthesis)

Stage of interphase where DNA is duplicated.

G2 (growth 2)

Second growth period of interphase, checking growth and environmental conditions.

Prophase

1st phase of mitosis where chromatin condenses into chromosomes.

Metaphase

2nd phase of mitosis where chromosomes align at the equatorial plate.

Anaphase

3rd phase of mitosis where centromeres split and chromosomes move to opposite poles.

Telophase

4th phase of mitosis where chromosomes reach poles and begin to uncoil.

Cleavage furrow

The indentation that begins to form in the cytoplasm during anaphase.

Daughter cells

Two identical cells formed from the division of a parent cell.

Mitosis duration

Usually completed in about twenty-four hours, with one to two hours spent in mitosis.

Somatic cells

Body type cells that undergo mitosis, such as skin, hair, and liver cells.

Gametes

Sex cells that are not somatic, including sperm and oocyte cells.

Mitosis consistency

During mitosis, chromosomes are duplicated and divided between daughter cells with great consistency.

Mutation

An alteration in the information within the DNA molecule that occurs occasionally (about once in every one million cell divisions).

Random mutations

Copying mistakes that occur during DNA replication; even DNA is not perfect.

Induced mutations

Mutations that are changed due to environmental factors, such as radiation, pollution, or cigarette smoke.

Missense mutation

A type of mutation that results in a different amino acid being incorporated into a protein.

Nonsense mutation

A mutation that creates a premature stop codon in the protein sequence.

Silent mutation

A mutation that does not change the amino acid sequence of a protein.

Insertion/deletion mutation

Mutations that involve the addition or loss of nucleotides in the DNA sequence.

Duplication mutation

A mutation that results in the duplication of a segment of DNA.

Frameshift mutation

A mutation caused by insertions or deletions that shift the reading frame of the genetic code.

Mutagenic factors

Factors that increase the mutation rate.

Common mutagens

Substances that may cause cancer, such as chemical agents (e.g., tobacco tar), radiation (e.g., UV and X-ray), and viruses.

Benign tumor characteristics

1) Usually localized (easily removed), 2) Grows slowly, 3) Encapsulated (sealed/doesn't spread quickly).

Malignant tumor characteristics

1) May not be localized, 2) Grows rapidly, 3) May not be encapsulated (may spread quickly).

Metastasis

The spreading of a primary tumor by blood vessels or lymph vessels to new areas to become secondary cancer masses.

Oncogene theory

Theories that describe how proto-oncogenes can become oncogenes, leading to rapid cell division and greater potential to cause cancer.

p53 gene

A gene that acts as an off switch, stopping cells with damaged DNA from dividing; if mutated, cells continue to divide.

Neoplasm

A term that means tumor.

Why is cancer so deadly?

1) Tumor cells are mostly immature and nonfunctional, 2) Tumor cells interfere with proper function of nearby systems, 3) Tumors may crowd organs and rob tissues of vital nutrients.

Stages of cancer

1 - 4, where stage 1 has the best probability of cure and stage 4 has the worst probability.

Cancer treatments

1) Surgery (best for localized, nonmetastasizing cancers), 2) Radiation (used to shrink tumor size), 3) Chemotherapy (chemicals toxic to rapidly dividing tumor cells).

Tissues

Groups of individual cells working together to perform a specific function.

Histology

The study of tissue structure.

Four distinct types of human tissue

1) Epithelial, 2) Connective, 3) Muscle, 4) Nervous.

Epithelial tissue

Covers surfaces, lines cavities and hollow organs, and forms glands.

Connective tissue

Fills, supports, covers body parts, stores fat, and transports (e.g., blood).

Muscle tissue

Contracts to provide movement of the body and organs.

Nervous tissue

Conducts impulses from organ to organ; used for communication.

blastocyst

a zygote (egg sperm combo) that has developed after about three weeks into development.

primary germ layers

several layers of tissue that develop from a blastocyst.

ectoderm

the primary germ layer that forms the nervous system, skin, sense organs, and some glands.

mesoderm

the primary germ layer that forms the skeleton, muscles, blood, kidneys, and most sex organs.

endoderm

the primary germ layer that forms the digestive, respiratory, and circulatory organs, and urinary bladder.

femur

the bone that is formed by the mesoderm.

ovaries

the reproductive organs that are formed by the mesoderm.

fingernails

the structures that are formed by the ectoderm.

trachea

the airway that is formed by the endoderm.

gall bladder

the organ that is formed by the endoderm.

epithelial tissues

tissues that cover body surfaces, line cavities and tubes, and comprise glands.

avascular

a characteristic of epithelial tissues indicating they have no blood supply and receive nutrients by diffusion.

basement membrane

the structure that anchors epithelial cells to underlying connective tissue.

basal lamina

the layer secreted by the epithelium that is part of the basement membrane.

reticular lamina

the layer secreted by the connective tissue that is part of the basement membrane.

squamous epithelium

a type of epithelial tissue where cells are flat and scale-like, specialized for diffusion or protection.

cuboidal epithelium

a type of epithelial tissue where cells are cube-shaped with a centrally located nucleus, specialized for secretion.

columnar epithelium

a type of epithelial tissue where cells are column-shaped with the nucleus in the lower third, specialized for absorption and some secretion.

transitional epithelium

a type of epithelial tissue that can change shape when stretched, found only in the urinary system.

simple epithelium

a type of epithelial tissue consisting of one layer of cells, good for diffusion.

stratified epithelium

a type of epithelial tissue consisting of two or more layers of cells, good for protection.

simple squamous epithelium

a single layer of thin flattened cells through which substances freely pass by secretion or diffusion, found in the lungs and blood vessels.

stratified squamous epithelium

composed of many layers of mostly flattened cells, may be up to sixty layers thick in some areas, providing protection against abrasion.

simple cuboidal epithelium

composed of a single layer of cube-shaped cells, primarily involved in secretion and some absorption.

Simple columnar epithelium

Composed of elongated cells whose nuclei are located near the basal portion of the cell.

Function of simple columnar epithelium

Functions in mostly absorption and some secretion in the digestive tract (and also in the female reproductive tract).

Cilia

Small, hair-like structures that move substances.

Goblet cells

Look like a cup and secrete mucus; they have no nuclei.

Pseudostratified (ciliated) columnar epithelium

Appears 'falsely' stratified because the nuclei are located at several levels within a single layer of cells that all touch the basement membrane.

Location of pseudostratified columnar epithelium

Lines the glottis (opening) of the upper respiratory tract among other locations.

Glandular epithelium

All glands are composed of epithelial cells that are specialized for secretion of hormones, neurotransmitters, breast milk, digestive enzymes, skin oils, tears, sweat, etc.

Classification of glands

Glands are classified by arrangement of cells, secretion location, and method of secretion.

Tubular glands

Secretory portion of the gland is tubular.

Alveolar glands

Secretory portion of the gland is alveolar.

Exocrine glands

Include a duct that opens onto a body surface.

Endocrine glands

Are 'ductless' glands that secrete contents into blood or lymph vessels.

Merocrine glands

Secretion of just a 'liquid' substance.

Serous type of secretion

'Watery' fluids, for example, salivary glands.

Mucous type of secretion

'Thick' fluids, for example, goblet cells.

Apocrine glands

Secretion is 'liquid' and top portion of the cell.

Holocrine glands

Secretion is liquid and the entire cell.

Classification of goblet cell

Goblet cells are classified as merocrine.

General characteristics of connective tissues

Acts to connect, support, bind, store fat, transport substances (blood).

Vascularity of connective tissues

Fat tissue and bone are very vascular; cartilage, ligaments, and tendons are avascular.

Extracellular matrix

Connective tissue is mostly extracellular matrix, which acts to separate the relatively few cells from each other.

Components of connective tissue

Connective tissue always has two components: cells (of several sorts) and extracellular matrix (nonliving).

Types of cells in connective tissue

Different cell types include fibroblast, chondrocytes, osteocytes, mast cells.

Areolar (loose) connective tissue

Cells are fibroblasts; fibers include elastic and collagen; functions to wrap and cushion.

Adipose tissue

Composed of specialized cells called adipocytes that have a large fat vacuole.

Locations of adipose tissue

Found in the hypodermis around blood vessels, abdomen, breasts, around eyes, and kidneys.

Functions of adipose tissue

Insulates, cushions, and stores energy.