Veterinary Embryology 8.1 - 8.4
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Veterinary Embryology 8.1 - 8.4 - Leaderboard
Veterinary Embryology 8.1 - 8.4 - Details
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| 🇬🇧 | 🇬🇧 |
| Obstetrics | Field of study concentrated on pregnancy, childbirth and the postpartum period |
| 3 Phases of Embryology | 1. Pre-Embryonic Period 2. Embryonic Phase 3. Fetal Phase |
| 4 Stages of the Embryonic Phase | 1. Fertilization 2. Cleavage 3. Gastrulation 4. Development of body form |
| Average length of the Embryonic Phase | 2-8 weeks (Depending on specie) |
| Fertilization | Sperm and ovum fuse to form a Zygote. (haploid + haploid = diploid) |
| Where does fertilization occur? | Uterine Tube |
| Name the glycoprotein layer that prevents additional sperm from entering the ovum after fertilization | Zona pellucida |
| Corona Radiata | Layer of follicular cells that surround the Zona Pellucida; does not impede fertilization; gradually desquamates to uncover nutrient pores in ZP |
| Zona pellucida | Glycoprotein layer that surrounds the ovum; becomes impermeable to sperm after fertilization |
| Factors that affect the rate at which cleavage occurs | 1) Quantity 2) Distribution of yolk in the ovum The presence of a large amount of yolk mechanically retards cleavage because yolk cannot divide as rapidly as cytoplasm can |
| Oligolecithal | Type of ova with a small amount of yolk (Mammalian Ova) |
| Isolecithal | Type of ova with yolk that is evenly distributed and nucleus is positioned centrally (Mammalian ova; resultant blastomeres are all the same size = cleavage is equal) |
| Where does cleavage begin and end? | Uterine tube; Uterus |
| Holoblastic | Complete cleavage that divides the whole egg into distinct and separate blastomeres (e.g. mammals) |
| Meroblastic | Incomplete cleavage as a result of the presence of an impeding mass of yolk material (e.g. eggs of birds) |
| At what cell stage does the embryo have a mulberry-like appearance? | 16-64 cell stage (known as a Merula) |
| Blastocyst cavity | Fluid filled cavity within the blastomere (Fluid filled spaced develop between the cells in the centre of the morula, they coalesce to form the blastocyst) |
| Trophoblast | 1. The membrane that forms the wall of the blastocyst in early development; aids implantation in the uterine wall Gives rise the the placenta |
| Embryoblast | Central cells (mainly from the animal pole) group together against the trophoblast to form the inner cell mass known as the Embryoblast Subsequently forms the embryo |
| Blastocyst | A structure formed in the early development of mammals. It possesses an inner cell mass (embryoblast) which subsequently forms the embryo. The outer layer of the blastocyst consists of cells collectively called the trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity known as the blastocyst cavity. |
| When is the Zona Pellucida lost in Ungulates? | After the Morula has been transformed into a blastocyst (Blastocyst looses is spherical shape after the loss of the ZP) |
| When is the Zona Pellucida lost in Carnivores? | After the commencement of gastrulation - at the stage when the somites start to form (Blastocyst looses is spherical shape after the loss of the ZP) |
| What is the shape and lenght of the ruminant blastocyst after the loss of the Zona Pellucida? | Narrow, tube like structure 50 cm + |
| What is the shape and lenght of the Pig blastocyst after the loss of the Zona Pellucida? | Narrow, tube like structure 1.5m |
| From what structure does the Embryonal Disc develop? | Embryoblast (The embryonal disc will later develop into the Embryo Proper) |
| Covering layer of Rauber | The part of the trophoblast that lies over the embryoblast. (Develops slower than the rest of the trophoblast) |
| Eutheria | Placental Mammals |
| Gastrulation | Differentiation of the 3 germ layers Transforms the unilaminar blastocyst into a trilaminar gastrula |
| Cleavage is controlled by... | Properties transferred by the maternal nucleus to the cytoplasm of the the zygote. |
| What does the Ectoderm layer differentiate into? | Reception of stimuli and protection of the organism |
| What does the Mesoderm layer differentiate into? | Support, movement, excretion and reproduction |
| What does the Endoderm layer differentiate into? | Digestion and respiration |
| Name the 4 stages of Gastrulation | 1. Formation of the Hypoblast and Embryonal disc 2. Primitive Streak Formation 3. Cell involution and Notochord Formation 4. Neurulation and Initial differentiation of the Mesoderm |
| When does Gastrulation commence? | After formation of the embryoblast |
| Hypoblast Formation | The hypoblast is a tissue type that forms from the inner surface of the embryoblast. It lies beneath the epiblast and consists of extended squamous epithelium. The hypoblast gives rise to the yolk sac, which in turn gives rise to the chorion. |
| Embryonal Disc Formation | After the loss of the Covering Layer of Rauber the exposed Embryoblast is transformed into a slightly convex layer of cells known as the Embryonal Disc. The Embryonal Disc is continues with the Trophoblast |
| Name the 2 layers of the Embryonal Disc | Hypoblast; Epiblast |
| What are the first 2 processes that occurs more or less simultaneously in the first stage of gastrulation? | Hypoblast Formation Embryonal Disc Formation |
| Name the 2 structures that are responsible for moving the cells destined to form the endoderm, mesoderm and ectoderm into their predefined areas within the epiblast | Primitive Streak Primitive Node |
| What phase of Gastrulation is the first step in the development of body cavities? | Primitive Streak Formation |
| Primitive streak formation | A dull, thickened stripe develops in the middle of the epiblast in the caudal half of the embryonal disc. It is formed by the medial and caudal migration of proliferating epiblast cells Continued cell migration causes cranial elongation of the primitive streak until it extends over all but the cranial third of the embryonal disc. |
| Primitive node | The caudal migration of proliferating epiblast cells from the cranial part of the embryonal disc causes a discrete aggregation of cells at the cranial end of the primitive streak; this thickening is known as the primitive node |
| Cell Involution | Proliferating cells immediately adjacent to the primitive streak are involuted into the area between the epi- and hypoblast The process of involution physically alters the primitive streak and it changes into a primitive groove, flanked on either side by a primitive fold. |
| Endoderm Formation | Some of the involuted cells invade the hypoblast and, multiply and form a layer on the deep surface of the embryonal disc known as the Embryonic Endoderm. |
| Extraembryonic Endoderm | Development if the endoderm displaces the hypoblast to the periphery of the Embryonic Disc. The Hypoblast now only lines the yolk sac and is now referred to as the EEE. |
| Involution gives rise to the formation of what 2 germ layers? | Endoderm; Mesoderm |
| Mesoderm Formation | The remaining involuted cells (i.e. those that did not invade the hypoblast to form the endoderm) now constitute the mesoderm. |
| In what anatomical directions does the mesoderm expand with continued cell involution and proliferation? | Cranially, caudally and laterally (excluding the area immediately cranial to the primitive node, the prechordal plate and the cloacal membrane. It expands beyond the periphery of the embryonal disc and between the trophoblast and extraembryonic endoderm of the entire yolk sac. |
| Embryonic Mesoderm | Mesoderm within the embryonal disc |
| Extra-embryonic mesoderm | Mesoderm beyond the periphery of the Embryonic Disc |
| The prechordal plate (circular area) is situated at the _____ edge of the embryonal disc and later forms the _______ membrane. | Cranial; Oropharyngeal |
| The mesoderm is prevented from invading the prechordal plate and the cloacal membrane by firm adhesion between the ________ and _______ | Epiblast and Endoderm (The area in front of the prechordal plate is, however, eventually invaded by the expanding mesoderm) |
| Where does the pleuropericardial coelom develop? | The area in front of the prechordal plate |
| Notochordal Process develops from the _____ | Primitive node |
| Notochordal canal | Lumen of the Notochordal Process |
| Primitive Pit is a indentation of the _______ _______ | Primitive Node |
| Neurulation | Notochord-induced transformation of ectoderm into nervous tissue |
| Notochord Formation | The notochord develops from the primitive node located at the cranial end of the primitive streak. From the node, cells proliferate and migrate forward into the future head region where they become the rod-shaped notochord. |
| The notochordal process extends between the ___ . | Epiblast and endoderm |
| Neurenteric canal | Temporarily connects the future amniotic cavity and yolk sac (Previously Notochordal canal) |
| Ectoderm Formation | All the epiblast cells that did not involute constitute the ectoderm |
| Neuro-ectoderm | The ectodermal cells on the dorsal midline Destined to form the future brain and spinal cord. |
| Neural Plate | Thickening of the Neuro-ectoderm cranial to the Primitive Node Wide, flat cranially = Future Brain Narrower in the middle, caudally = future spinal chord |
| Neural Groove | Dorsal surface of the neural plate invaginates forming the NG |
| Neural Folds | Borders the Neural Groove on either side |
| Neural Tube | Neural folds fuse along the dorsal midline to form the NT The lumen of the NT is the Neural Canal |
| Neural Canal | Lumen of the Neural Tube Temporarily communicates with the amnotic cavity via the rostral and caudal neuropores. The rostral neuropore closes last. |
| Neuropore | Rostral or Caudal opening of the Neural Tube Temporarily communicates with the amniotic cavity. (Rostral opening closes last.) |
| That part of the neural tube destined to form the brain bends ________, enlarges and forms three vesicles; these vesicles are the primordia of the ______, _____ and _____ | Ventrally Prosencephalon, Mesencephalon and Rhombencephalon |
| Name the structure that causes ventral bending of the Neural Tube at the level of the Mesencephalon. | Cephalic Flexure |
| Name the structure that causes ventral bending of the Neural Tube at the junxtion between the Rhombencephalon and the Spinal Chord. | Cervical Flexure |
| After the formation of the future brain from the Neural Tube, the remaining NT forms the ______ | Spinal Chord |
| What structure remains as the central canal of the spinal chord and continues rostrally with the _____ ventricle. | Neural Canal; Fourth (in the Rhombencephalon) |
| Sulcus Limitans | From the level of the mesencephalon, a longitudinal groove develops bilaterally in the walls of the neural canal. |
| Paraxial Mesoderm | Distinct longitudinal columns adjacent to the Notochord (Originates from mesoderm) |
| Lateral Mesoderm | Mesoderm peripheral to Paraxial Mesoderm |
| Numerous _____ _____ that divide the paraxial mesoderm into blocks known as somites. | Transverse Fissures |
| Somite development progresses in a _____ direction, with the first somite forming just ___ to the ___ end of the notochord. | Cranio-caudal; caudal; rostral |
| What structure is used to estimate embryonal age? | Number of Somites |
| Tissues that somites give rise to include ... | Bone Muscle Dermis |
| The coelom splits the lateral mesoderm into two layers, namely... | Somatic and Splanchnic Mesoderm |