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Embryology
| Question | Answer |
|---|---|
| IgA (Immunoglobulin A): | An antibody found mainly in mucosal secretions (such as saliva, tears, and intestinal fluids) that helps protect body surfaces exposed to the external environment. |
| IgE (Immunoglobulin E): | An antibody involved in allergic reactions and defense against parasitic infections by triggering mast cells and basophils to release inflammatory mediators. |
| IgG (Immunoglobulin G): | The most abundant antibody in blood and tissues, providing long-term protection against infections and capable of crossing the placenta to protect the fetus. |
| IgD (Immunoglobulin D): | An antibody found primarily on the surface of immature B cells, where it functions as a receptor involved in B-cell activation and development. |
| IgM (Immunoglobulin M): | The first antibody produced during an initial immune response, highly effective at binding pathogens and activating the complement system. |
| What are the 6 layers of the egg (outermost to innermost)? | Corona Radiata → Zona Pellucida (vitelline membrane in non-mammals) → Perivitelline Space → Plasma Membrane → Nucleus and other organelles → Cortical granules |
| What are the 3 parts of sperm? | Headpiece (acrosome + nucleus), Mid-piece, Tail (flagella) |
| What is capacitation? | Biochemical process initiated by secretions in the uterus and fallopian tubes to make sperm more active in the female reproductive tract |
| What are the 6 steps of fertilization? | 1) Sperm penetrates corona radiata 2) Reaches zona pellucida 3) Acrosome reaction digests zona pellucida 4) Sperm fuses with egg plasma membrane 5) Sperm nucleus enters egg 6) Two haploid nuclei fuse → diploid zygote (2n) |
| What is the fast block to polyspermy? | Occurs instantaneously when sperm fuses with plasma membrane; sodium channels open causing Na⁺ influx, depolarizing the egg membrane and preventing other sperm from binding for a short time |
| What is the slow block to polyspermy? | Depolarization causes Ca²⁺ release from the ER → cortical granules fuse with membrane and release contents into perivitelline space → zona pellucida detaches and hardens into the fertilization membrane, blocking future sperm |
| What happens after the slow block? | A second meiotic division of the egg is completed |
| What happens during cleavage? | Rapid mitotic cell division increases cell number by 2ⁿ but cytoplasm amount stays the same (no cell growth) |
| What is determinate (mosaic) cleavage? | Cell fate is decided early in development; separated blastomeres cannot form a complete organism |
| What is indeterminate (regulative) cleavage? | Cell fate is determined later; if a blastomere is removed, both it and the remaining embryo can form complete organisms (twins) |
| What is radial cleavage? | New cells form directly above previous cells |
| What is spiral cleavage? | New cells form at an angle to previous cells |
| Compare protostomes vs. deuterostomes across 4 features. | Cleavage direction: Spiral vs. Radial | Cleavage type: Determinate vs. Indeterminate | First formation: Mouth vs. Anus | Coelom: Schizocoelus vs. Enterocoelus |
| What is determination? | When a cell has decided which genes will be expressed and which will be repressed |
| What is differentiation? | A visible physical change in a cell expressing certain genes; observable under a microscope |
| Does differentiation change the genome? | No — every cell retains all genes; differentiation is selective expression only |
| What is the developmental sequence from fertilized zygote? | Fertilized zygote → Morula → Blastula → Gastrula → Neurula |
| What is a morula? | A solid ball of cells |
| What is a blastula? What is it called in humans? | A hollow sphere of cells; in humans it is called a blastocyst |
| What happens during gastrulation? | Blastula cells invaginate via a blastopore (becomes mouth in protostomes, anus in deuterostomes); embryo develops 3 germ layers (ectoderm, mesoderm, endoderm); different parts of embryo interact for the first time; a gut tube forms |
| What does ectoderm give rise to? | Epidermis (skin/hair), adrenal medulla, jaw + teeth, sensory system, nervous system |
| What does endoderm give rise to? | Epithelial lining of GI tract, respiratory tract, excretory system, reproductive tract; thyroid, parathyroid, thymus; liver |
| What does mesoderm give rise to? | Circulatory system, lymphatic system, skeletal system, muscular system, adrenal cortex, notochord |
| What is embryonic induction? | A cell influencing the development of nearby cells; confirmed by transplanting embryo parts and observing new structure formation |
| Example of induction? | Transplanting an additional notochord causes a second neural tube to develop; optic vesicle induces lens formation in surface ectoderm |
| What are the 3 steps of neurulation? | 1) Notochord stimulates overlying ectoderm to thicken (induction) forming the neural plate 2) Neural plate folds inward 3) Neural plate forms and pinches off as the neural tube |
| What does the notochord become? | Parts of the intervertebral discs and spinal vertebrae |
| What does the neural tube become? | The brain and spinal cord |
| What are the 4 key features all chordates have during development? | Dorsal hollow nerve cord, notochord, pharyngeal gill slits, post-anal tail |
| What are the 4 steps of amphibian embryology? | 1) Sperm fuses with animal pole 2) Embryo rotates 30°, forming the gray crescent opposite sperm entry 3) Gray crescent foretells future body pattern 4) Early cleavage cells require a portion of the gray crescent to develop into a complete organism |
| What are amniotes and what do they have? | Birds, reptiles, and mammals; develop specialized membranes outside the embryo including a fluid-filled amnion |
| What are non-amniotes? | Amphibians and fish; lack amnion and extraembryonic layers; lay eggs in water |
| What are monozygotic twins? | One sperm fertilizes one egg → 1 zygote → 2 genetically identical embryos |
| What are dizygotic twins? | 2 eggs fertilized by 2 sperm → regular siblings born at the same time |
Created by:
smurtab