BIOL1410: Units 1 to 5 - Anatomy, Chemistry, Cells, Cell Cycle, and Early Human Development

Anatomy

The study of internal and external body structures and the relationships between structures (e.g., bone and muscle).

Microanatomy

The subdivision of anatomy that requires a microscope to view structures, including cytology (the study of cells) and histology (the study of tissues).

Histology

The study of tissues, which are groups of structurally similar cells that perform a common function.

Gross Anatomy

The subdivision of anatomy that examines structures visible to the unaided eye, such as bones, the heart, the stomach, and body cavities (e.g., cranial, thoracic, abdominopelvic).

Organ

A structural level of organization composed of two or more tissues working together to accomplish a common function (e.g., the stomach, which contains all four major tissue types for digestion).

Organ System

A level of organization consisting of several related organs that cooperate to accomplish a common purpose (e.g., the respiratory system, consisting of the lungs, larynx, trachea, and other organs).

Isotopes

Different structural forms of an atom in which the number of neutrons is not equal to the number of protons and electrons.

Electrolytes (Ions)

Atoms that have gained or lost electrons and become charged; they include cations such as $Ca^{2+}$, $Na^+$, $K^+$, and $H^+$, and anions such as $Cl^-$.

Ionic Bond

A chemical bond formed by the atom-to-atom transfer of electrons between cations and anions (e.g., $NaCl$).

Covalent Bond

A chemical bond formed by the sharing of electrons between atoms (e.g., $O_2$).

Organic Substances

Compounds containing covalently bonded carbon ($C$) atoms, such as carbohydrates, proteins, lipids, and nucleic acids.

Inorganic Substances

Chemical substances that usually lack carbon atoms (such as $H_2O$, salts, and $O_2$), with specific exceptions including $H_2CO_3$, $HCO_3^-$, $CO_2$, and $CO$.

Acid

A substance that dissociates in $H_2O$ to release $H^+$ ions, where an increase in hydrogen ion concentration causes a decrease in pH ($\uparrow [H^+] = \downarrow \text{pH}$).

Base

A substance that binds to or buffers free $H^+$ ions in $H_2O$, leading to a decrease in hydrogen ion concentration and an increase in pH ($\downarrow [H^+] = \uparrow \text{pH}$).

pH Scale

A measure of the concentration of free $H^+$ in solution ranging from $0$ (acidic) to $7$ (neutral) to $14$ (basic/alkaline), with normal blood pH maintained between $7.35$ and $7.45$.

Monosaccharides

Simple sugars with the general formula $(CH_2O)_n$ (such as glucose, fructose, ribose, and deoxyribose) that serve as basic building blocks of other carbohydrates.

Phospholipids

Molecules composed of a polar, hydrophilic phosphate head group, a glycerol backbone, and two non-polar, hydrophobic fatty acid tails.

Adenosine Triphosphate (ATP)

A modified $RNA$ nucleotide composed of adenosine (ribose and adenine) and three phosphate groups ($\text{Adenosine}-P\sim P\sim P$) that powers cellular activities when high-energy bonds ($\sim$) are broken.

Plasma Membrane

The boundary separating intracellular fluid (ICF) from extracellular fluid (ECF), composed of a phospholipid bilayer, cholesterol, membrane proteins, and outer carbohydrates.

Transmembrane Proteins

Integral membrane proteins that have hydrophobic regions and extend across the entire width of the plasma membrane.

Microvilli

Small projections of the cell membrane that increase surface area, best observed on cells of the small intestine and kidney.

Fluid Mosaic Model

A model describing the cell membrane as a fluid structure where phospholipids and some proteins move around, while proteins dot the surface like tiles in a mosaic.

Cytosol

The gel-like intracellular fluid of the cytoplasm containing water, ions (e.g., $K^+$, $Na^+$), suspended nutrients, and cellular inclusions like melanin or glycogen.

Centrosome

An organizing center for microtubules consisting of a pair of centrioles and pericentriolar matrix, responsible for forming the spindle apparatus and organizing the cytoskeleton.

Microfilaments

Cytoskeletal elements composed of actin that function in muscle contraction (alongside myosin), cell locomotion, and cytokinesis.

Microtubules

Hollow cytoskeletal tubes composed of tubulin that form centrioles, the spindle apparatus, cilia, and flagella, and move or secure organelles in place.

Rough Endoplasmic Reticulum (RER)

A membranous network studded with ribosomes that specializes in the synthesis of secretory, lysosomal, and membrane proteins.

Smooth Endoplasmic Reticulum (SER)

A membranous network continuous with the RER that lacks attached ribosomes and synthesizes lipids and steroid hormones.

Golgi Apparatus

Stacks of membrane discs that modify, sort, package, and deliver proteins to the cell membrane, lysosomes, or for extracellular secretion.

Lysosomes

Membranous organelles filled with digestive enzymes that degrade bacteria, viruses, and worn-out organelles.

Nucleolus

A dense, non-membranous nuclear region of $DNA$, $RNA$, and proteins where ribosomes are made and assembled.

Chromatin

The dispersed, uncoiled form of $DNA$ and histone proteins that is not individually visible, representing the state of $DNA$ during most of a cell's life when not dividing.

Gametes

Haploid ($n$) reproductive cells containing $23$ different chromosomes, consisting of ova (eggs) and sperm.

Somatic Cells

All non-germ cells of the body containing $46$ chromosomes ($23$ homologous pairs), characterized as diploid ($2n$).

Homologous Chromosomes

A pair of chromosomes (one inherited from each parent) that are highly similar in length and centromere position, carrying genes for the same traits at identical loci.

Alleles

Alternative versions of a gene on homologous chromosomes that code for proteins producing alternate phenotypic versions of a trait.

Autosomes

Chromosomes numbered $1$ to $22$ that carry genes coding for somatic characteristics (e.g., hair colour, eye colour, height).

$G_0$ Phase

A non-dividing state observed in mature cells that permanently remain in $G_1$ and do not divide again (e.g., nerve cells and some muscle cells).

S Phase

The synthesis phase of interphase during which chromosomes replicate into sister chromatids joined at a centromere.

Kinetochore

A protein complex formed on each centromere of a sister chromatid ($1$ per chromatid) that serves as the attachment point for spindle microtubules.

Mitosis

The process of somatic nuclear division that separates replicated chromosomes into two genetically identical sets across prophase, metaphase, anaphase, and telophase.

Cytokinesis

The division of the cytoplasm that begins during anaphase and concludes during or immediately following telophase.

Tetrad

A four-chromatid structure formed during Prophase I of meiosis when homologous chromosomes pair and attach together.

Meiosis I

The reduction division of reproductive nuclear division in which homologous chromosome pairs (tetrads) separate, halving the chromosome number from diploid ($2n$) to haploid ($n$).

Meiosis II

The second nuclear division of meiosis in which sister chromatids separate without intervening $DNA$ replication, yielding four genetically unique haploid gametes.

Zygote

A single diploid ($2n$) cell with $46$ chromosomes formed by the fusion of a haploid ($n$) sperm with a haploid ($n$) ovum in the uterine tube.

Cleavage Divisions

The series of $4 - 5$ mitotic divisions undergone by the zygote that produce the morula without increasing the overall size of the structure.

Morula

A solid ball of $16 - 32$ cells that forms during the pre-embryonic period and remains the same physical size as the original ovum or zygote.

Blastocyst

A developmental structure composed of a fluid-filled blastocoel cavity, an inner embryoblast (inner cell mass), and an outer trophoblast layer.

Implantation

The attachment of the blastocyst to the endometrium of the uterine wall after traveling from the uterine tube.

Epiblast

The layer of the bilayered embryonic disc that undergoes mitosis to produce the amnion (and amniotic cavity) and all three primary germ layers.

Hypoblast

The layer of the bilayered embryonic disc that undergoes mitosis to generate the yolk sac.

Ectoderm

The embryonic germ layer derived from epiblast cells that develops into the nervous system and the epidermis of the skin.

Mesoderm

The embryonic germ layer derived from epiblast cells that gives rise to muscles, the cardiovascular system, the dermis of the skin, and most bones.

Endoderm

The embryonic germ layer derived from epiblast cells that forms the epithelial linings of the digestive, respiratory, urinary, and reproductive systems, along with associated glands.

Chorion

An extraembryonic membrane derived from trophoblast cells that surrounds all other embryonic membranes and develops chorionic villi containing blood vessels to form the fetal part of the placenta.

Amnion

An extraembryonic membrane derived from epiblast cells that encloses the fluid-filled amniotic cavity, providing shock absorption and temperature regulation for the developing embryo/fetus.

Allantois

An extraembryonic membrane projection off the yolk sac that contributes to the formation of the umbilical cord and the urinary bladder.

Fetal Period

The developmental timeframe spanning from the $9\text{th}$ week to the end of the $40\text{th}$ week, characterized by the growth and maturation of pre