Human Embryology - Week 6 Development
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What significant development occurs in the brain during the fifth week of embryonic development?

  • The hindbrain merges with the forebrain.
  • The midbrain becomes fully developed.
  • The forebrain divides into the telencephalon and diencephalon. (correct)
  • Cranial nerves stop forming.

    • Which structures begin to form for future sensory organs during the fifth week?

  • Optic vesicles for eyes and otic pits for inner ears. (correct)
  • Cranial bones for protection and lung buds for respiration.
  • Laryngeal structures for sound and palate for taste.
  • Nasal cavities for smell and limb buds for movement.

    • What is the approximate size of an embryo during the fifth week of development?

  • 10-12 mm
  • 7-9 mm (correct)
  • 3-5 mm
  • 15-17 mm

    • What role do somites play in embryonic development?

    <p>They contribute to the development of the musculoskeletal system.</p> Signup and view all the answers

    Which cardiovascular changes occur during the fifth week?

    <p>Septation begins in the heart chambers.</p> Signup and view all the answers

    What is the main function of the thalamus during embryonic development?

    <p>Processing and relaying sensory information.</p> Signup and view all the answers

    Which primary brain vesicle remains undivided during the fifth week?

    <p>Midbrain</p> Signup and view all the answers

    What happens to the upper limb buds by the fifth week of development?

    <p>They develop into paddle-shaped structures.</p> Signup and view all the answers

    What is the primary role of the metencephalon in hindbrain differentiation?

    <p>Develops into the cerebellum</p> Signup and view all the answers

    Which cranial nerves originate from the forebrain?

    <p>CN I and II</p> Signup and view all the answers

    What process occurs to form the interventricular septum during heart development?

    <p>Upward growth from the base of the heart</p> Signup and view all the answers

    What is the significance of the foramen secundum in fetal circulation?

    <p>Ensures continued blood flow in fetal circulation</p> Signup and view all the answers

    Which structure is responsible for controlling involuntary activities such as breathing and heartbeat?

    <p>Medulla oblongata</p> Signup and view all the answers

    What marks the transition of the heart from a simple tubular structure to a complex organ by week 5?

    <p>Establishment of systemic and pulmonary circulation</p> Signup and view all the answers

    Which statement accurately describes cranial nerve formation?

    <p>Cranial nerves play a role in higher brain functions and coordination</p> Signup and view all the answers

    What is the primary function of the endocardial cushions in the atrioventricular canal?

    <p>To form the tricuspid and mitral valves</p> Signup and view all the answers

    What occurs during the development of endocardial cushions?

    <p>Development of valves in the atrioventricular canal</p> Signup and view all the answers

    Which structure is responsible for dividing the truncus arteriosus into the aorta and pulmonary trunk?

    <p>Conotruncal ridges</p> Signup and view all the answers

    What is the outcome of incomplete septation in the heart development?

    <p>Persistence of the interventricular foramen</p> Signup and view all the answers

    During eye development, which structure emerges as lateral bulges from the diencephalon?

    <p>Optic vesicles</p> Signup and view all the answers

    Which feature distinguishes the inner layer of the optic cup?

    <p>It develops into the neural retina</p> Signup and view all the answers

    What role do neural crest cells play in heart development?

    <p>Formation of the conotruncal ridges</p> Signup and view all the answers

    What initiates the formation of the lens during eye development?

    <p>Thickening of surface ectoderm at the lens placode</p> Signup and view all the answers

    What is the function of the Apical Ectodermal Ridge (AER) in limb development?

    <p>Facilitates outgrowth and differentiation of mesoderm in limb buds</p> Signup and view all the answers

    At what embryonic level do upper limb buds begin to form?

    <p>Somite level C4-T1</p> Signup and view all the answers

    Which aspect of the interventricular septum development is essential for proper heart function?

    <p>Division of the left and right ventricles</p> Signup and view all the answers

    Which structure is induced by signals from the underlying optic vesicle?

    <p>Lens vesicle</p> Signup and view all the answers

    What type of cells form the precursor to the inner ear during development?

    <p>Ectodermal cells</p> Signup and view all the answers

    What is a key feature of the development of otic vesicles?

    <p>They pinch off from deepening otic pits</p> Signup and view all the answers

    What is the main role of the core mesoderm in upper limb buds?

    <p>Forms skeletal structures, muscles, and connective tissue</p> Signup and view all the answers

    How do lower limb buds compare to upper limb buds in terms of development timing?

    <p>They begin forming slightly after upper limb buds</p> Signup and view all the answers

    What signifies the importance of the cochlea developed from otic vesicles?

    <p>Establishes a foundation for hearing</p> Signup and view all the answers

    Study Notes

    Human Embryology - Week 6 Embryo Development

    • This lesson details embryo development during the fifth week.
    • Students will be able to describe key events, including brain, heart, and limb bud growth.
    • Somites' role in musculoskeletal system development will be explained.
    • Cardiovascular development, including early circulation pathways and vessel formation, will be identified.
    • The formation of major organs and systems, such as respiratory and digestive, during this stage will be described.

    Week 5 Embryonic Development Overview

    • Rapid brain and head development occurs.
    • Organ primordia become more defined.
    • Approximate size: 7-9 mm
    • Brain development: Division of the primary brain vesicles (forebrain, midbrain, hindbrain). Cranial nerves begin forming.
      • Eye development: Optic vesicles appear (future eyes). Otic pits form (future inner ears).
    • Limb development: Upper limb buds become paddle-shaped, with lower limb buds appearing. Heart development: Septation begins in the heart chambers.

    Embryonic Period Overview

    • Duration: First 8 weeks after conception.
    • Major embryological events: Organs formed from three primary germ tissues, emergence of basic body plan.
    • Timelines: 25 days (3 weeks), 3.5 mm; 36 days (5 weeks), 10 mm; 56 days (8 weeks), 30 mm

    Week 5 Brain and Cranial Nerve Development Summary

    • Brain Vesicles: Forebrain (Telencephalon - cerebrum; Diencephalon -thalamus and hypothalamus), Midbrain, Hindbrain (Metencephalon- pons, cerebellum; Myelencephalon- medulla)..
    • Midbrain: Relay center for sensory & motor functions.
    • Hindbrain: Controls involuntary activities (breathing, heartbeat).

    Forebrain (Prosencephalon) Differentiation

    • Division into two regions:
      • Telencephalon: Forms the future cerebral hemispheres, involved in advanced brain functions (cognition, memory, and voluntary movements).
      • Diencephalon: Develops into the thalamus and hypothalamus, with the thalamus acting as a sensory relay center and the hypothalamus regulating autonomic functions (temperature and hormonal control).

    Midbrain (Mesencephalon) Week 5

    • Midbrain remains undivided in week 5. A critical relay center, processing visual and auditory information, coordinating reflexive responses to stimuli.
    • Acts as a connection between the forebrain and hindbrain, later forming structures like the tectum and tegmentum.

    Hindbrain (Rhombencephalon) Differentiation

    • Division into two regions:
      • Metencephalon: Forms the pons (connects cerebellum to other brain parts), and the cerebellum (coordinates motor functions and balance).
      • Myelencephalon: Becomes the medulla oblongata (controls involuntary activities like breathing and heartbeat).
    • Essential for vital body functions and motor coordination.

    Cranial Nerves

    • CN I (olfactory) and CN II (optic) from the forebrain.
    • CN III-XII from the midbrain and hindbrain.
    • Lay the foundation for higher brain functions, sensory pathways, and motor coordination.

    Heart Development: Week 5

    • Heart undergoes complex morphogenesis to form four chambers.
    • Key Events:
      • Septation of Atria:
        • Septum primum grows from the atrial roof
        • Formation of foramen primum and secundum
      • Septation of Ventricles:
        • Interventricular septum grows from the heart base
        • Separates primitive left and right ventricles
    • Endocardial Cushion Formation: Cushions develop in atrioventricular canal, contributing to valve formation
    • Conotruncal Septation: Truncus arteriosus divides into the aorta and pulmonary trunk.

    Overview of Heart Development

    • Transition from a simple tubular structure to a complex organ with chambers and valves.
    • Establishment of the groundwork for systemic and pulmonary circulation.
    • Key processes: Septation of atria and ventricles, formation of endocardial cushions and valves, division of the truncus arteriosus, blood flow and anatomical descriptions.

    Eye and Ear Development: Week 5

    • Eye development
      • Optic Vesicles: Appear as lateral bulges from the diencephalon, forming the optic cup which gives rise to the retina and optic nerve.
      • Lens Placode: Thickening of surface ectoderm, precursor to the lens.
    • Ear development
      • Otic Pits: Invaginations of surface ectoderm lateral to the hindbrain forming otic vesicles which are precursors to the inner ear structures (cochlea, semicircular canals).

    Limb Development in Week 5

    • Upper Limb Buds: Appear as paddle-shaped structures derived from mesoderm (skeletal precursors), covered by ectoderm
    • Lower Limb Buds: Appear slightly later than the upper limb buds, starting at the caudal end of the embryo.
    • Apical Ectodermal Ridge (AER): specialized ectoderm at the distal tip of limb buds, essential for promoting outgrowth and differentiation of underlying mesoderm.

    Role of Apical Ectodermal Ridge (AER)

    • AER acts as the primary signalling center for limb development, promoting proliferation of mesodermal cells and ensuring outgrowth and limb patterning along the proximal-distal axis.
    • Fibroblast Growth Factors (FGF) are secreted by AER to maintain mesoderm proliferation and differentiation.

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    BIU Human Embryology Lesson 04 Development Week 06 PDF

    Description

    Explore the key events of embryo development during Week 6. This quiz covers brain, heart, and limb bud growth, as well as the formation of major organs and systems. Gain insights into the role of somites in the musculoskeletal system and early cardiovascular development.

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