The document describes the development of an embryo through various stages from fertilization to organ formation:
1) It starts as a zygote that undergoes cleavage to form a blastula, then a gastrula with three germ layers.
2) The neural tube forms from the ectoderm along with the notochord.
3) Various organs and structures develop such as the brain dividing into regions like the telencephalon and diencephalon, and gills forming in the pharynx.
4) Later stages show the heart forming chambers and arches while lungs, kidneys and other organs emerge from the mesoderm and endoderm.
I am rajan an school teacher by profession with post graduation in English,psychology,economics and post graduate diploma in teaching English have been working in a school for 25 years,a remote village in kerala I came in this field not by chance as many in our
place but deliberately.I like this profession very much But I have very limited like minded people to share my views.I want to discuss with such people
Fruit flies swarm in every orchard during the hot months. They thrive on the fruits that fall premature from the tree. August through October, you can also find them buzzing around any bowl of fruit on your kitchen table. They especially love bananas
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
I am rajan an school teacher by profession with post graduation in English,psychology,economics and post graduate diploma in teaching English have been working in a school for 25 years,a remote village in kerala I came in this field not by chance as many in our
place but deliberately.I like this profession very much But I have very limited like minded people to share my views.I want to discuss with such people
Fruit flies swarm in every orchard during the hot months. They thrive on the fruits that fall premature from the tree. August through October, you can also find them buzzing around any bowl of fruit on your kitchen table. They especially love bananas
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
introduction to cranial nerve, olfactory nerve, olfactory bulb, course of orlfactory nerve, termination in the cerebral cortex, functional component of cranial nerve
cortex, a region filled with a highly cellular connective tissue stroma and many ovarian follicles, which in the adult ovary vary greatly in size The most internal part of the ovary is the medulla, which contains loose connective tissue and blood vessels entering the organprimordial follicles—consist of a primary oocyte enveloped by a single layer of the flattened follicular cellsunilaminar primary follicle stratified follicular epithelium, the granulosa, in which the cells communicate through gap junctions. Follicle cells are now termed granulosa cells and the follicle is a multilayered primary follicle (cuboidal cells)
Multilaminar Primary FolliceZonapellucida:four glycoproteins secreted by the oocyte;bind proteins on the surfaces of sperm and induce acrosomal activation. Filopodia of follicular cells and microvilli of the oocyte penetrate the zonapellucida, allowing communication between these cells via gap junctions.
Each ovary is covered by a simple cuboidal epithelium, the germinal epithelium, continuous with the mesothelium and overlying a layer of dense connective tissue capsule, the tunica albugineagranulosa layer as the cells secrete follicular fluid accumulates, the spaces gradually coalesce antrum Follicular Fluid : hyaluronate, growth factors, plasminogen, fibrinogen, the anticoagulant heparansulfate proteoglycan, and high concentrations of steroids (progesterone, androstenedione, and estrogens) with binding proteins.Membranagranulosa (columnar)
Follicular WallsGranulosa Cells – Stratified ColumnarBM – separates TI and GTI: vacuolated and lightly stained because of their cytoplasmic lipid droplets, a characteristic of steroid-producing cells (androstenedione which is transformed in the granulosa cells as estradiol)TE: fibroblasts and smooth muscle cells continuous with stroma
Corpus luteum after ovulation (super folded)Corpus Albicans: scar of dense connective tissue called corpus albicans in the absence of pregnancy (less convoluted)
After ovulation:Granulosa cells granulosa lutein cellsaromatase conversion of androstenedione into estradiolTheca interna cells Theca lutein cells stain more darkly, with cytoplasmic ultrastructural features of steroid-synthesizing cells stimulated by LH
Atretic follicle: oocyte is detached from granulosa cellsAtresia involves apoptosis and detachment of the granulosa cells, autolysis of the oocyte and collapse of the zonapellucida. Early in this process, macrophages invade the degenerating follicle and phagocytose the debris. Occurs anytime
Mature OocyteAchievement of Polarity and Radial Symmetry
Frog OvarySource of Yolk: Digested FoodYolk Nuclei from germinal vesicle
Unfertilized egg
Second Cleavage furrow relatively shallow compared to first
Yolk is resistant to cleavage forces
CoeloblastulaEpidermal layer (highly pigmented) Skin Epithelium or Lining of nervous systemNervous Layer Neuroblasts of the Nervous SystemMarginal Zone: active conversion of yolk to cytoplasm; involved in formation of the lips of the blastoporeStill seen is the fertilization membrane (not labeled)
CoeloblastulaEpidermal layer (highly pigmented) Skin Epithelium or Lining of nervous systemNervous Layer Neuroblasts of the Nervous SystemMarginal Zone: active conversion of yolk to cytoplasm; involved in formation of the lips of the blastoporeStill seen is the fertilization membrane (not labeled)
Process: InvolutionVentral limit of the gray crescent region of formation of the dorsal lip of the blastopore
Ring of involuted marginal zone (lip) cells are collectively known as the yolk plugInvoluted dorsal lip cells endodermMore ventral and lateral to the chordamesoderm is the mesodermChordamesoderm notochord
notochord was derived from cells indistinguishable from the mesoderm at the region of the dorsal lipSomites become: 1. Dermatome dermis and appendage musculature 2. Sclerotome vertebral skeleton 3. Myotome skeletal musclesSomatic mesoderm in conjuction with the ectoderm skin with its blood and connective tissuesSplanchnic mesoderm in conjuction with gut endoderm lining epithelium, muscles, and blood vessels of the entire mid- and hindgut.