Week 1: The cell chapter 7 Histology and Embryology

Q: What is histology?

A: The study of cells and tissues and how they function

Why study histology?

A: Because we work with and manipulate different tissues in the body.

What is the smallest unit?

The cell

Q: List key cell functions.

A: Absorption, assimilation, respiration, irritability, conductivity, growth, reproduction, excretion.

Q: What are common cell components?

A: Nucleus, nucleolus, cell membrane, cytoplasm, organelles.

Q: Do cells vary in size, shape, structure, and function?

A: Yes, cells vary widely in all of these characteristics.

Q: What is active transport?

A: Energy-requiring processes that move substances across the membrane.

Q: Define exocytosis.

removal of materials out of the cell by fusing of a vesicle membrane with the cell membrane

Q: Define endocytosis.

A:uptake of materials into the cell via membrane invagination.

Q: What is pinocytosis?

A: "Cell drinking" — uptake of fluids.

Q: What is phagocytosis?

A: "Cell eating" — uptake of larger particles. 🍽️

Q: What is the cell membrane composed of?

A: A phospholipid bilayer and proteins.

Q: Role of proteins in the membrane?

A: Structural reinforcement and receptors for hormones, neurotransmitters, and immunoglobulins.

Q: What does semipermeable mean?

A: The membrane selectively allows certain substances in/out.

Q: What is cytoplasm (cytosol)?

A: Jelly-like fluid inside the membrane containing organelles, inclusions, and vacuoles.

Q: Function of cytoplasm?

A: Medium in which organelles function.

Q: What are inclusions?

A: Metabolically inert, temporary cell components (e.g., glycogen, lipids, melanin). ⏳

Q: What are organelles?

A: Metabolically active, specialized structures enabling the cell to function per its genetic code.

Q: List major organelles.

A: Nucleus, mitochondria, ribosomes, ER, Golgi apparatus, lysosomes, cytoskeleton.

Q: Is the nucleus present in all cells?

A: In all except mature RBCs and platelets.

Q: What are binucleated cells? Give examples.

A: Cells with two nuclei; examples: cardiac muscle cells, parenchymal liver cells.

Q: What are multinucleated cells? Give examples.

A: Cells with multiple nuclei; examples: osteoclasts, skeletal muscle cells.

Q: What does the nucleus produce?

A: DNA (genetic info) and RNA (carries info to sites of protein synthesis).

Q: What is the nucleolus?

A: Structure in the nucleus that produces rRNA and nucleotides of other RNAs.

Q: What is chromatin?

A: DNA in diffuse form containing chromosomes; appears as stippling at low power.

Q: What is nucleoplasm?

A: The fluid inside the nucleus containing proteins.

Q: What is the nuclear envelope?

A: A double-layered membrane surrounding the nucleus.

Q: What are ribosomes made of and what do they do?

A: Protein and RNA; they synthesize proteins ("protein factories"). 🏗️

Q: What is the endoplasmic reticulum (ER)?

A: Interconnected membrane-bound channels linked to the cell membrane, nuclear membrane, and organelles.

Q: Primary functions of ER?

A: Modification, storage, segregation, and transport of proteins.

Q: What is rough ER (RER)?

A: ER with ribosomes; site of protein synthesis for further processing.

Q: What is smooth ER (SER)?

A: ER without ribosomes; synthesizes lipids and steroid hormones.

Q: What is the Golgi apparatus?

A: Stack of 3-20 flattened sacs; the cell's "chemical processing and packaging center."

Q: Functions of the Golgi apparatus?

A: Sorts, condenses, packages, and delivers proteins from RER; releases contents by exocytosis.

Q: What are mitochondria?

A: The "powerhouses" of the cell; numerous organelles with two membranes (inner folded into cristae).

Q: Function of mitochondria?

A: Release energy from food and produce ATP (adenosine triphosphate).

Q: What are lysosomes?

A: Membranous sacs from the Golgi containing hydrolytic and digestive enzymes (e.g., hyaluronidase). They digest substances and worn-out parts.

Q: What are the components of the cytoskeleton?

A: Microfilaments, intermediate filaments, microtubules.

Q: General functions of the cytoskeleton?

A: Provides stability, maintains cell shape, and creates "freeways" for molecular movement.

Q: What are microfilaments and their function?

A: Thin protein fibers; enable cell movement and motility (e.g., myofibrils in muscle).

Q: What are microtubules and their function?

A: Long, stiff tubes; maintain cell shape and form structures like cilia, flagella, centrioles, and the mitotic spindle.

Q: Difference between cilia and flagella?

A: Cilia are shorter and numerous; flagella are longer and few.

Q: What are intermediate filaments? Example?

A: Thicker threadlike fibers; example: tonofilaments in intercellular junctions.

Q: What are tight junctions and where are they found?

A: Fused membranes that close intercellular spaces, preventing fluid movement; found in small intestinal lining.

Q: What are desmosomes and where are they found?

A: "Spot welds" binding adjacent cells; found in outer skin and oral mucosa.

Q: What are hemidesmosomes and their role?

A: Attach cells to non-cellular surfaces (half-desmosome); attach epithelium to connective tissue (e.g., basement membrane) and gingiva to tooth.

Q: What are gap junctions and where are they found?

A: Tubular channels allowing exchange of substances; found in heart muscle and digestive tube.

Q: What are the main stages of the cell life cycle?

A: Interphase, mitosis, cytokinesis, and differentiation. (Meiosis occurs in sex cell maturation.)

Q: What happens in interphase?

A: Cell grows and forms new organelles; period between mitoses.

Q: What occurs in G1 phase?

A: Initial growth (resting) phase.

Q: What occurs in S phase?

A: DNA replication (chromatin) and centrosome replication.

Q: What occurs in G2 phase?

A: Second growth (resting) phase; ends as mitosis begins.

Q: What is mitosis?

A: Division of nuclear parts into two equal daughter nuclei.

Q: What happens in prophase?

A: Chromatin condenses; centrioles move to poles; nuclear membrane and nucleolus disappear.

Q: What happens in metaphase?

A: Chromosomes align midway; spindle fibers attach to centromeres.

Q: What happens in anaphase?

A: Centromeres split; chromatids separate and move to opposite poles; spindle fibers shorten.

Q: What happens in telophase?

A: Two daughter nuclei form; chromosomes decondense to chromatin; nuclear membranes and nucleoli reappear; microtubules disappear.

Q: What is cytokinesis?

A: Division of the cytoplasm into two identical daughter cells following mitosis.

Q: What is cellular differentiation?

A: Process by which a less specialized cell becomes a more specialized cell type. Example: ovum + sperm → fetus.