March 11, 2010
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The Yolk-sac

The yolk-sac (Figs. 90022 and 90023) is situated on the ventral aspect of the embryo; it is lined by entoderm, outside of which is a layer of mesoderm. It is filled with fluid, the vitelline fluid, which possibly may be utilized for the nourishment of the embryo during the earlier stages of its existence. Blood is conveyed to the wall of the sac by the primitive aortæ, and after circulating through a wide-meshed capillary plexus, is returned by the vitelline veins to the tubular heart of the embryo. This constitutes the vitelline circulation, and by means of it nutritive material is absorbed from the yolk-sac and conveyed to the embryo. At the end of the fourth week the yolk-sac presents the appearance of a small pear-shaped vesicle (umbilical vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct. The vesicle can be seen in the after-birth as a small, somewhat oval-shaped body whose diameter varies from 1 mm. to 5 mm.; it is situated between the amnion and the chorion and may lie on or at a varying distance from the placenta. As a rule the duct undergoes complete obliteration during the seventh week, but in about three per cent. of cases its proximal part persists as a diverticulum from the small intestine, Meckel’s diverticulum, which is situated about three or four feet above the ileocolic junction, and may be attached by a fibrous cord to the abdominal wall at the umbilicus. Sometimes a narrowing of the lumen of the ileum is seen opposite the site of attachment of the duct.

Fig. 90022– Human embryo of 2.6 mm. (His.)

Fig. 90023– Human embryo from thirty-one to thirty-four days. (His.)

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Gray's Anatomy

Complete Image List

1. Embriology

Embriology Image List

The Animal Cell

The Spermatozoön

Fertilization of the Ovum

Segmentation of the Fertilized Ovum

The Neural Groove and Tube

The Primitive Segments

Separation of the Embryo

Development of the Fetal Membranes and Placenta

The Branchial Region

Development of the Body Cavities

The Form of the Embryo at Different Stages of Its Growth

2. Osteology

Osteology Image List

Vertebral Column

General Characteristics of a Vertebra Cervical Vertebra Thoracic Vertebra Lumbar Vertebra Sacral and Coccygeal Vertebra Vertebral Column as a Whole Sternum Ribs Costal Cartilages Thorax

Skull

Introduction Exterior SkullSuperior view Anterior view Orbit Lateral view Posterior view Inferior view Interior SkullIntroduction & Skull Cap Anterior Cranial Fossa Middle Cranial Fossa Posterior Cranial Fossa Nasal cavity Mandible Hyoid Bone

Cranial Bones

Occipital Bone Sphenoid Bone Temporal Bones Parietal Bones Frontal Bone Ethmoid Bone Inferior Nasal Concha Lacrimal Bones Nasal Bones Vomer Sutural Bones

Facial Bones

Maxilla Palatine Bone Zygomatic Bone Differences in Skull due to Age Sex Differences in Skull & Craniology

Extremities

Extremities Upper Extremity BonesScapula Clavicle Humerus Radius Ulna HandSkeleton of the Hand Carpals Metacarpals Phalanges of the Hand Ossification of bones of the Hand Lower Extremity BonesHip Bone Pelvis Femur Patella Tibia Fibula FootSkeleton of the Foot Tarsals Metatarsals Phalanges of the Foot Ossification of bones of the Foot Comparison of the Bones of the Hand and Foot Sesamoid Bones

3. Arthrology

Arthrology Image List

Classification of Joints

Movements Permitted at Joints

Trunk Articulations

Mandibular joint (temporomandibular joint) Vertebral Column ArticulationsJoints of the Vertebral Bodies Joints of the Vertebral Arches Sacrococcygeal Joint Atlantoaxial Articulation (C1-C2)Vertebral Column with the Cranium Costovertebral Articulations Sternocostal Articulations Interchondral Articulations Sternal Articulations Mechanism of the Thorax

Upper Extremity Articulations

Sternoclavicular (SC) Joint Acromioclavicular (AC) Joint Ligaments of the Scapula Shoulder Joint (glenohumeral – GH)Elbow Joint Radioulnar Joints Radiocarpal Joints (wrist-joint)Intercarpal Articulations Carpometacarpal & Intermetacarpal Articulations Metacarpophalangeal Articulations Interphalangeal Joints

Pelvis Articulations

Sacroiliac (SI) Joints Pubic Symphysis Mechanism of the Pelvis

Lower Extremity Articulations

Hip-joint (acetabulofemoral joint - AF)Knee joint Tibiofibular Joints Ankle-joint (talocrural)Intertarsal Articulations Tarsometatarsal & Intermetatarsal Articulations Metatarsophalangeal & Interphalangeal Articulations Arches of the Foot

4. Myology

Myology Image List

Introductions & Definitions

Mechanics of Muscle

Tendons, Aponeuroses, and Fascia

Muscles of the Head

Muscles of the Scalp Muscles of the Eyelid Muscles of the Nose Muscles of the Mouth Muscles of Mastication Muscles of the Anterolateral Region of the NeckAnterolateral Region Superficial & Lateral Cervical Muscles Supra and Infrahyoid Muscles Anterior Vertebral Muscles Lateral Vertebral Muscles

Muscles of the Trunk

Deep Muscles of the Back Suboccipital Muscles Muscles of the Thorax Mechanism of Respiration Muscles and Fascia of the Abdomen Muscles and Fascia of the Pelvis Muscles and Fascia of the Perineum Muscles of the Urogenital Region - Male Muscles of the Urogenital Region - Female

Muscles of the Upper Extremity

Muscles Connecting the Upper Extremity to the Vertebral Column Muscles Connecting the Upper Extremity to the Thoracic Walls Muscles and Fascia of the Shoulder Muscles and Fascia of the Arm Muscles and Fascia of the Forearm Muscles and Fascia of the Hand

Muscles of the Lower Extremity

Muscles and Fascia of the Iliac Region Muscles and Fascia of the ThighAnterior Femoral Muscles Medial Femoral Muscles Muscles of the Gluteal Region Posterior Femoral Muscles Muscles and Fascia of the LegAnterior Shin (crural) Muscles Posterior Crural Muscles Lateral Crural Muscles Fascia Around the Ankle Muscles and Fascia of the Foot

5. Angiology

Angiology Image List

Development of the Vascular System

Thoracic Cavity

Introduction Pericardium Heart Peculiarities in the Vascular System in the Fetus

6. The Arteries

Arteries Image List

Arteries of the Head and Neck

a) Common Carotid ArteryRelations External Carotid Artery Triangles of the Neck Internal Carotid Artery b) Arteries of the Brain

Arteries of the Upper Extremity

Subclavian Artery Axilla Axillary Artery Brachial Artery Radial Artery Ulnar Artery

Arteries of the Trunk

Descending Aorta Thoracic Aorta Abdominal Aorta Common Iliac Arteries Hypogastric Artery External Iliac Artery

Arteries of the Lower Extremity

Femoral Artery Popliteal Fossa Popliteal Artery Anterior Tibial Artery Dorsalis Pedis Artery Posterior Tibial Artery

7. The Veins

Veins Image List

Pulmonary Veins

Systemic Veins

Veins of the Heart Veins of the Head and NeckVeins of the Exterior of the Head and Face Veins of the Neck Diploic Veins Veins of the Brain Venous Sinuses of the Dura Mater (Opthalmic and Emissary Veins)Veins of the Upper Extremity and Thorax Veins of the Lower Extremity, Abdomen, and Pelvis

Portal System of Veins

8. The Lymphatic System

Lymphatic System Image List

Lymphatics of the Head, Face, and Neck

Lymphatics of the Upper Extremity

Lymphatics of the Lower Extremity

Lymphatics of the Abdomen and Pelvis

Lymphatic Vessels of the Thorax

9. Neurology

Neurology Image List

Structure of the Nervous System

Development of the Nervous System

Spinal Cord or Medulla Spinalis

Brain or Encephalon

Introduction Hind-brain or Rhombencephalon Mid-brain or Mesencephalon Fore-brain or Prosencephalon Composition and Central Connections of the Spinal Nerves Composition and Central Connections of the Spinal Nerves 2 Pathways from the Brain to the Spinal Cord Meninges of the Brain and Medulla Oblongata (Spinalis)Cerebrospinal Fluid

Cranial Nerves

Introduction 1. Olfactory Nerves 2. Optic Nerve 3. Oculomotor Nerve 4. Trochlear Nerve 5. Trigeminal Nerve 6. Abducent Nerve 7. Facial Nerve 8. Acoustic Nerve 9. Glossopharyngeal Nerve 10. Vagus Nerve 11. Accessory Nerve 12. Hypoglossal Nerve

Spinal Nerves

Introduction Posterior Divisions Anterior Divisions Thoracic Nerves Lumbosacral Plexus Sacral and Coccygeal Nerves

Sympathetic Nerves

Introduction Cephalic Portion of the Sympathetic System Cervical Portion of the Sympathetic System Thoracic Portion of the Sympathetic System Abdominal Portion of the Sympathetic System Pelvic Portion of the Sympathetic System Great Plexuses of the Sympathetic System

10. The Organs of the Senses and the Common Integument

Organs Image List

The Peripheral Organs of the Special Senses

a. The Organs of Taste b. The Organ of Smell c. The Organ of Sight 1. The Tunics of the Eye 2. The Refracting Media 3. The Accessory Organs of the Eye d. The Organ of Hearing 1. The External Ear 2. The Middle Ear or Tympanic Cavity 3. The Auditory Ossicles 4. The Internal Ear or Labyrinth e. Peripheral Terminations of Nerves of General Sensations

The Common Integument

11. Splanchnology

Splanchnology Image List

The Respiratory Apparatus

The Respiratory Apparatus a. The Larynx b. The Trachea and Bronchi c. The Pleurae d. The Mediastinum e. The Lungs

The Digestive Apparatus

The Digestive Apparatus a. The Mouth b. The Fauces c. The Pharynx d. The Esophagus e. The Abdomen f. The Stomach g. The Small Intestine h. The Large Intestine i. The Liver j. The Pancreas

The Urogenital Apparatus

a. Development of the Urinary and Generative OrgansDevelopment of the Urinary and Generative Organs b. The Urinary Organs 1. The Kidneys 2. The Ureters 3. The Urinary Bladder 4. The Male Urethra 5. The Female Urethra c. The Male Genital Organs 1. The Testes and their Coverings 2. The Ductus Deferens 3. The Vesiculae Seminales 4. The Ejaculatory Ducts 5. The Penis 6. The Prostate 7. The Bulbourethral Glands d. The Female Genital OrgansThe Female Genital Organs 1. The Ovaries 2. The Uterine Tube 3. The Uterus 4. The Vagina 5. The External Organs 6. The Mammae

The Ductless Glands

a. The Thyroid Gland b. The Parathyroid Glands c. The Thymus d. The Hypophysis Cerebri e. The Pineal Body f. The Chromaphil and Cortical Systems g. The Spleen

12. Surface Anatomy and Surface Markings

Surface Image List

Surface Anatomy of the Head and Neck

Surface Markings of Special Regions of the Head and Neck

Surface Anatomy of the Back

Surface Markings of the Back

Surface Anatomy of the Thorax

Surface Markings of the Thorax

Surface Anatomy of the Abdomen

Surface Markings of the Abdomen

Surface Anatomy of the Perineum

Surface Markings of the Perineum

Surface Anatomy of the Upper Extremity

Surface Markings of the Upper Extremity

Surface Anatomy of the Lower Extremity

Surface Markings of the Lower Extremity

Muscle Tables

Muscles of facial expression Muscles of mastication Eye movement Palate Pharynx Larynx Tongue muscles Hyoid Muscles Anterior & Lateral Neck Prevertebral Posterior Neck Muscles Superficial back Deep back Shoulder muscles Arm muscles Anterior Forearm Posterior Forearm Hand muscles Thoracic wall Anterior abdominal wall Posterior abdominal wall Pelvic floor muscles Gluteal region Posterior thigh Anterior thigh Medial thigh Anterior & lateral leg Posterior leg Foot

Quizzes

1. Introduction

Anatomical Terms Body Regions Skeleton Introduction Bones Hand-Foot Landmarks Joint Classifications Actions Muscle Shapes Muscles Introduction

2. Head & Face

Bones Muscles Introduction Muscles of Eye Movement

3. Neck

Bones Ligaments Muscles Introduction Scalenes Deep anterior neck Posterior Neck

4. Torso

Trunk Bones Anterior Trunk Torso Joints Abdominal Muscles Introduction Back Muscles Introduction Back Muscles Superficial Back Muscles Deep Back Muscles Transversospinalis Vertebrae Detailed

5. Shoulder & Arm

Bones Ligaments Shoulder Muscles Arm Muscles Rotator Cuff Muscles

6. Forearm, Wrist & Hand

Bones Ligaments Anterior Muscles Introduction Posterior Muscles Introduction Thenar Muscles Central Hand Muscles Hypothenar Muscles

7. Hip, Thigh & Knee

Bones Ligaments Gluteal Muscles Intro Posterior Thigh Intro Medial Thigh Intro Anterior Thigh Intro

8. Leg, Ankle & Foot

Bones Ligaments Anterior Leg Muscles Lateral Leg Muscles Posterior leg Superficial Posterior Leg Deep Foot Muscles

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